Method of treating cancer and method of sensitizing cancer cells to the action of chemotherapeutic agents via growth hormone receptor antagonists or knock down

ABSTRACT

Various aspects of the present invention relate to a method of treating cancer in a subject having cancer cells, wherein the cancer cells possess at least one growth hormone receptor, and wherein the method includes controlling an action of the growth hormone receptor. In various non-limiting embodiments, controlling an action of the growth hormone receptor may occur via knock down of the growth hormone receptor, or may be caused by inhibiting growth hormone action, such as via the use of antibodies directed against growth hormone or the growth hormone receptor. Methods may also relate to administering an antagonist of the growth hormone receptor, and administering at least one anti-tumor drug in concert with administration of the antagonist. Another aspect may include a method of maintaining an anti-tumor drug in cancer cells of a subject by controlling an action of at least one growth hormone receptor in the cancer cells.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. patent application Ser. No.16/464,742, filed May 29, 2019, which is a U.S. national phase filingunder 35 U.S.C. § 371 of International Patent Application No.PCT/US2017/064188, filed Dec. 1, 2017, which claims priority to and thebenefit of the filing date of U.S. Patent Application Ser. No.62/429,273, filed Dec. 2, 2016, the disclosures of which areincorporated by reference herein in their entireties.

FIELD OF THE INVENTION

The present invention relates generally to methods of treating cancers,and more specifically to methods of treating cancer via interferencewith growth hormone receptor.

BACKGROUND OF THE INVENTION

This section is intended to introduce the reader to various aspects ofart that may be related to various aspects of the present invention,which are described and/or claimed below. This discussion is believed tobe helpful in providing the reader with background information tofacilitate a better understanding of various aspects of the presentinvention. Accordingly, it should be understood that these statementsare to be read in this light, and not as admissions of prior art.

Melanoma (a word derived from the Greek words—melas, “dark” and oma“tumor”) is an ancient disease, dating back to 5^(th) century BC withthe earliest physical evidence found in the 2,400-year-old mummies ofthe pre-Colombian era. In modern times, melanoma is considered the mostaggressive and treatment-resistant form of human skin cancer, with anannual incidence of 73,870 in 2015 with a total of approximately1,000,000 patients in the USA. The estimated mortality from melanoma inthe US in 2015 is 9,970 and includes children, adolescents and adults.Fair skinned people have the highest propensity to acquire melanoma,with males (28.2%) having a higher predisposition than females (16.8%).More than 10,000 men and women in the United States and 60,000 worldwideare expected to die of melanoma in 2016, which globally claims aboutfive lives per hour.

The number of new cases annually has been rising steadily in the last 30years, during which the five-year survival rate increased from 86%(1985) to 93% (2012), albeit with a poor quality of life. Studiesindicate increased UV exposure, use of tanning beds, hormone replacementtherapies as well as improved and increased diagnostic screening, as theunderlying causes of heightened melanoma incidence. Melanoma usuallyoccurs in the exposed parts of the body—face, neck, hands and feet—butcan also be found in any anatomical site occupied by melanocytes, likethe gastrointestinal, genitourinary and respiratory mucosa, and thechoroidal layers of the eye.

Chemotherapeutic interventions for melanoma often result in drugresistance that may occur by several cellular mechanisms. Thedevelopment of a melanoma vaccine has enjoyed limited success. However,in the last five years, a number of highly efficacious immunotherapies,e.g. CTLA-4 antibody, ipilimumab; PD-1/PD-L1 antibody, andpembrolizumab, and targeted therapies, e.g. V600E BRAF inhibitor andvemurafenib, have been approved by the FDA. Several additionaltherapeutic regimens are in various stages of development. In spite ofthese promising advancements in melanoma therapy, some areas of concernremain. For instance, effective therapy with one of the most successfulmelanoma drugs, pembrolizumab, requires pre-existence of activecytotoxic T-cells in the system while resistance to most other knownchemotherapies, including ipilimumab and vemurafenib, has been reported.

Indeed, melanoma is unique among other types of cancers in possessingmultiple robust mechanisms of chemotherapeutic resistance. This includesabundant expression of a repertoire of drug efflux pumps, melanosomalsequestration of drugs in melanosomes during melanogenesis, as well asupregulation of epithelial-mesenchymal transition (EMT) markers.However, molecular mechanisms to define melanoma drug-resistance arelacking.

SUMMARY OF THE INVENTION

Certain exemplary aspects of the invention are set forth below. Itshould be understood that these aspects are presented merely to providethe reader with a brief summary of certain forms the invention mighttake and that these aspects are not intended to limit the scope of theinvention. Indeed, the invention may encompass a variety of aspects thatmay not be explicitly set forth below.

As described above, cancers, such as melanoma, may possess robustmechanisms of chemotherapeutic resistance. And molecular mechanisms todefine such drug resistance are lacking. However, as now elucidated bythe present inventors, reducing the effects of growth hormone (GH) maybe used to prevent and/or treat cancer in a subject. And so, one aspectof the present invention may include a method of treating cancer in asubject having cancer cells, wherein the method includes reducing one ormore effects of growth hormone. Further, any mechanism to reduce theeffects of GH may be used. Exemplary mechanisms include growth hormonereceptor knock down (GHR-KD), administering antibodies against GH and/orgrowth hormone receptor (GHR), and administering GHR antagonists, amongothers. GHR-KD may be accomplished by administering small interferingRNA (siRNA) sequences to the subject, but other methods of GHR-KD may beused.

Thus, one aspect of the present invention may include a method oftreating cancer in a subject having cancer cells, wherein the cancercells include at least one growth hormone receptor, and wherein themethod includes controlling an action of the growth hormone receptor.Further, one aspect of the present invention may include a method oftreating cancer in a subject having cancer cells, wherein the cancercells include at least one growth hormone receptor, and wherein themethod includes controlling an action of the growth hormone receptor viaknock down of the growth hormone receptor.

Another aspect of the present invention may include a method of treatingcancer in a subject having cells including at least one growth hormonereceptor, wherein the method includes controlling an action of thegrowth hormone receptor, and administering a sub-EC₅₀ dose of at leastone anti-tumor drug.

Another aspect of the present invention may include a method of treatingcancer in a subject having cells including at least one growth hormonereceptor, wherein the method includes controlling an action of thegrowth hormone receptor by administering an antagonist of the growthhormone receptor, and administering at least one anti-tumor drug inconcert with administration of the antagonist.

Another aspect of the present invention may include a method of treatingcancer in a subject having cancer cells, said cancer cells including atleast one growth hormone receptor, wherein the method includescontrolling an action of the growth hormone receptor, wherein thecontrolling an action of the growth hormone receptor is caused byinhibiting growth hormone action. This inhibition may be effected viathe use of antibodies (such as antibodies directed against the growthhormone receptor, or antibodies directed against growth hormone.

Another aspect of the present invention may include a method of treatingcancer in a subject having cancer cells, said cancer cells possessing atleast one growth hormone receptor, wherein the method includes reducingserum insulin-like growth factor 1 (IGF1) levels below the normal serumIGF1 level of the subject.

Another aspect of the present invention may include a method ofmaintaining an anti-tumor drug in cancer cells of a subject bycontrolling an action of at least one growth hormone receptor in thecancer cells. In this aspect of the present invention, the controllingof an action of the growth hormone receptor may include: knock down ofthe growth hormone receptor; co-administration of an antagonist of thegrowth hormone receptor with the anti-tumor drug; inhibiting growthhormone action via antibodies directed against growth hormone; orinhibiting growth hormone action via antibodies directed against thegrowth hormone receptor.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate embodiments of the invention and,together with the general description of the invention given above andthe detailed description of the embodiments given below, serve toexplain the principles of the present invention.

FIG. 1 includes microphotographs showing siRNA transfection efficiencyin SK-MEL-28 cells [plated at 10,000 cells/cm² and treated with either20 nM GHR-specific siRNA (siRNA-A—1 b, 2 b; siRNA-B—1 c,2 c; siRNA-C, 1d, 2 d) or scramble-siRNA (1 e,2 e); with untreated cells being treatedwith only transfection reagent (1 a, 2 a)]. Cy3 labelled scramblereporter siRNA was used to confirm transfection.

FIGS. 2A-2C include graphs showing the siRNA optimization for theprocess of GHR knock-down (KD) on melanoma cell proliferation, with FIG.2A showing SK-MEL-28 cells, FIG. 2B showing MALME-3M cells, and FIG. 2Cshowing SK-MEL-5 cells.

FIGS. 3A-3C include graphs showing that GHR RNA and protein levels aresuppressed following siRNA mediated KD in melanoma cells.

FIG. 4 includes microphotographs showing that GHR expression isabrogated following siRNA mediated KD in melanoma cells (top left tobottom right—SK-MEL-28, MALME-3M, MDA-MB-435, SK-MEL-5).

FIG. 5 includes microphotographs and graphs showing that growth hormonereceptor knock-down (GHR-KD) attenuates invasive properties in humanmelanoma cell (SK-MEL-28).

FIG. 6 includes further microphotographs and graphs showing that growthhormone receptor knock-down (GHR-KD) attenuates migration andclonogenicity in human SK-MEL-28 melanoma cells.

FIG. 7 includes microphotographs and graphs showing that GHR knock-downattenuates migration and invasion in human melanoma cells—MALME-3M,MDA-MB-435, and SK-MEL-5.

FIGS. 8A-8B include graphs showing that GH-excess promotes, while GHR-KDattenuates human melanoma cell proliferation

FIGS. 9A-9I include photographs and graphs showing that GH-excesspromotes, and GHR-KD attenuates, multiple oncogenic intracellularsignaling pathways in human melanoma cells.

FIGS. 10A-10L include graphs showing a comparison of changes in RNAlevel expression of key components of GH/IGF-1 axis in MALME-3M cells.

FIGS. 11A-11I include graphs and photographs showing that GH-excesspromotes, and GHR-KD attenuates, phosphorylation levels of multiplecritical intracellular signaling pathways in human melanoma cells.

FIGS. 12A-12B include graphs showing RT-qPCR analysis of GH-IGF axis inhuman melanoma cells.

FIGS. 13A-13L include graphs showing a comparison of changes in RNAlevel expression of key components of GH/IGF-1 axis in SK-MEL-5 cells.

FIGS. 14A-14B include graphs and photographs showing a change in markersof DNA damage following GHR-KD.

FIG. 15 includes graphs and photographs showing a change in markers ofapoptosis following GHR-KD.

FIG. 16 includes graphs and photographs showing the effect of GHR knockdown (KD) on melanoma cell migration.

FIGS. 17A-17C include graphs showing RT-qPCR analysis of GH-GHR andPRL-PRLR pairs in human melanoma cells.

FIGS. 18A-18F include graphs showing RT-qPCR analysis of components ofIGF axis in MALME-3M cells.

FIGS. 19A-19F include graphs showing RT-qPCR analysis of components ofIGF axis in MDA-MB-435 cells.

FIGS. 20A-20F include graphs showing RT-qPCR analysis of components ofIGF axis in SK-MEL-5 cells.

FIGS. 21A-21D include graphs showing that GH-excess increases and GHR-KDdecreases HGF, MET, ERBB3 RNA-levels in human melanoma cells.

FIGS. 22A-22D include graphs showing the effect of GHR-KD on ABCB1expression following drug treatment in human melanoma cells.

FIGS. 23A-23D include graphs showing the effect of GHR-KD on ABCB5expression following drug treatment in human melanoma cells.

FIGS. 24A-24D include graphs showing the effect of GHR-KD on ABCB8expression following drug treatment in human melanoma cells.

FIGS. 25A-25D include graphs showing the effect of GHR-KD on ABCC1expression following drug treatment in human melanoma cells.

FIGS. 26A-26D include graphs showing the effect of GHR-KD on ABCC2expression following drug treatment in human melanoma cells.

FIGS. 27A-27D include graphs showing the effect of GHR-KD on ABCG1expression following drug treatment in human melanoma cells.

FIGS. 28A-28D include graphs showing the effect of GHR-KD on ABCG2expression following drug treatment in human melanoma cells.

FIGS. 29A-29C include graphs and photographs showing a change in ABCtransporter pumps following GHR-KD.

FIGS. 30A-30C include graphs showing the effect of GHR excess on ABCB8,ABCC1, ABCC2 and ABCG2 expressions following drug treatment in humanmelanoma cells.

FIGS. 31A-31C include graphs showing the effect of GHR excess on ABCB1,ABCB5, and ABCG1 expressions following drug treatment in human melanomacells.

FIGS. 32A-32H include graphs showing that regulators of melanogenesispathway are influenced by GH action in melanoma cells.

FIGS. 33A-33L include graphs showing that markers of EMT are stronglymodulated by GH action in melanoma cells.

FIGS. 34A-34D include graphs and photographs showing a change in markersof epithelial mesenchymal transition (EMT) following GHR-KD.

FIGS. 35A-35D include graphs showing that GHR-KD resulted in increaseddrug retention and drastically reduced proliferation of melanoma cells.

FIG. 36 includes microphotographs showing the effect of drug treatmenton level of Ki-67-cell proliferation marker in SK-MEL-28 cells followingGHR-KD and drug treatment.

FIG. 37 includes microphotographs showing the effect of drug treatmenton level of Ki-67-cell proliferation marker in MALME-3M cells followingGHR-KD and drug treatment.

FIG. 38 includes microphotographs showing the effect of drug treatmenton level of Ki-67-cell proliferation marker in MDA-MB-435 cellsfollowing GHR-KD and drug treatment.

FIG. 39 includes microphotographs showing the effect of drug treatmenton level of Ki-67-cell proliferation marker in SK-MEL-5 cells followingGHR-KD and drug treatment.

FIGS. 40A-40E include graphs showing that bGH induced higher RNAexpression of ABCB1, ABEG1, and ABEG2 in bGH mice (high serum GH)compared to wild-type (WT) littermates.

FIGS. 41A-41D include graphs showing in vivo genotypic changes in ABCefflux pump expressions in B16-F10 mouse melanoma xenografted in mousemodels of high circulating G—bGH and GHR-KD.

FIGS. 42A-42F include graphs showing in vivo genotypic changes inmarkers of epithelial-to-mesenchymal transition (EMT) in B16-F10 mousemelanoma xenografted in mouse models of high circulating G—bGH andGHR-KD.

FIGS. 43A-43B includes photographs showing lower protein levelexpression of epithelial marker Cdh1 in female GHRKO mice, and higherAbcg2 level in GHRKO male mice composed to wild-type littermates.

FIG. 44 includes graphs showing the effect of exogenous GH inupregulating, and the effect of GHR antagonists in suppressing,expression of ABC transporters and markers of EMT in human liver cancercell—HepG2.

FIG. 45 includes graphs showing the effect of GHR antagonist on HGFlevels and MET levels in human liver cancer cells—HepG2 cells andSK-HEP-1.

FIG. 46 includes photographs showing that GH increases thephosphorylation states of STAT3, STAT5, SRC, and ERK1/2 in human livercancer cells—HepG2 cells and SK-HEP-1.

FIG. 47 includes graphs showing that, in human melanoma cells SK-MEL-28,an increase in transcript levels of markers of EMT is observed insynchrony with an increase in autocrine GH and in GHR levels followingaddition of a chemotherapeutic agent.

FIG. 48 includes graphs showing that, in human melanoma cells SK-MEL-28,an increase in transcript levels of ABC-type multi-drug efflux pumps isobserved in synchrony with an increase in autocrine GH and in GHR levelsfollowing addition of a chemotherapeutic agent.

FIG. 49 includes schematic representations of the mechanism of action ofGH-GHR regulated drug resistance in cancer cells and how attenuating theGHR by an antagonist would reverse it and sensitize the cancer cell tochemotherapeutics.

DETAILED DESCRIPTION

One or more specific embodiments of the present invention will bedescribed below. To provide a concise description of these embodiments,all features of an actual implementation may not be described in thespecification. It should be appreciated that in the development of anysuch actual implementation, as in any engineering or design project,numerous implementation-specific decisions must be made to achieve thedevelopers' specific goals, such as compliance with system-related andbusiness-related constraints, which may vary from one implementation toanother. Moreover, it should be appreciated that such a developmenteffort might be complex and time consuming, but would nevertheless be aroutine undertaking of design, fabrication, and manufacture for those ofordinary skill having the benefit of this disclosure.

As described above, reducing the effects of growth hormone (GH) may beused to prevent and/or treat cancer in a subject. And so, one aspect ofthe present invention may include a method of treating cancer in asubject having cancer cells, wherein the method includes reducing one ormore effects of growth hormone. Further, any mechanism to reduce theeffects of GH may be used. Exemplary mechanisms include growth hormonereceptor knock down (GHR-KD), administering antibodies against GH and/orgrowth hormone receptor (GHR), and administering GHR antagonists, amongothers. GHR-KD may be accomplished by administering small interferingRNA (siRNA) sequences to the subject, but other methods of GHR-KD may beused.

Thus, one aspect of the present invention may include a method oftreating cancer in a subject having cancer cells, wherein the cancercells including at least one growth hormone receptor, and wherein themethod includes controlling an action of the growth hormone receptor.Further, one aspect of the present invention may include a method oftreating cancer in a subject having cancer cells, wherein the cancercells including at least one growth hormone receptor, and wherein themethod includes controlling an action of the growth hormone receptor viaknock down of the growth hormone receptor.

In this aspect of the present invention, the subject may be a human incertain embodiments. And, while the aspects of the present invention arecontemplated for treating cancer in general, and many different types ofcancers more specifically, in certain embodiments, the cancer to betreated may be chosen from breast cancer, colorectal cancer, prostatecancer, hepatic cell carcinoma, and melanoma.

Further, as described above, the method of this aspect of the presentinvention may involve controlling an action of a growth hormone receptorvia knock down of the growth hormone receptor. In particularembodiments, the knock down of the growth hormone receptor may beperformed by siRNA mediated knock down. And, in further embodiments, theknock down of the growth hormone receptor may be via anti-sense RNAdirected against the growth hormone receptor. In yet furtherembodiments, the knock down of the growth hormone receptor may be causedby an antibody specific to the growth hormone receptor.

Another aspect of the present invention may include a method of treatingcancer in a subject having cells including at least one growth hormonereceptor, wherein the method includes controlling an action of thegrowth hormone receptor, and administering a sub-EC₅₀ dose of at leastone anti-tumor drug.

In this aspect of the present invention, (like the previous aspectdescribed above), the subject may be a human in certain embodiments.And, while the aspects of the present invention are contemplated fortreating cancer in general, and many different types of cancers morespecifically, in certain embodiments, the cancer to be treated may bechosen from breast cancer, colorectal cancer, prostate cancer, hepaticcell carcinoma, and melanoma.

Further in this aspect of the present invention, while it iscontemplated that the method may be amenable for use with any anti-tumordrug (or any of a number of anti-tumor drugs), in certain embodiments,the anti-tumor drug may be chosen from cisplatin, doxorubicin, oridonin,paclitaxel, and vemurafenib.

Further, as described above, the method of this aspect of the presentinvention may involve controlling an action of a growth hormone receptorvia knock down of the growth hormone receptor. In particularembodiments, the knock down of the growth hormone receptor may beperformed by siRNA mediated knock down. And, in further embodiments, theknock down of the growth hormone receptor may be via anti-sense RNAdirected against the growth hormone receptor. In yet furtherembodiments, the knock down of the growth hormone receptor may be causedby an antibody specific to the growth hormone receptor.

Further, the controlling an action of the growth hormone receptor maydirectly lead to inhibiting growth hormone action. And, this may becaused in turn by antibodies directed against growth hormone.

Further, the controlling an action of the growth hormone receptor mayinclude administering an antagonist of the growth hormone receptor. And,in certain embodiments, the antagonist of the growth hormone receptormay be pegvisomant.

Another aspect of the present invention may include a method of treatingcancer in a subject having cells including at least one growth hormonereceptor, wherein the method includes controlling an action of thegrowth hormone receptor by administering an antagonist of the growthhormone receptor, and administering at least one anti-tumor drug inconcert with administration of the antagonist.

In this aspect of the present invention, (like the previous aspectsdescribed above), the subject may be a human in certain embodiments.And, while the aspects of the present invention are contemplated fortreating cancer in general, and many different types of cancers morespecifically, in certain embodiments, the cancer to be treated may bechosen from breast cancer, colorectal cancer, prostate cancer, hepaticcell carcinoma, and melanoma.

Further in this aspect of the present invention, while it iscontemplated that the method may be amenable for use with any anti-tumordrug (or any of a number of anti-tumor drugs), in certain embodiments,the anti-tumor drug may be chosen from cisplatin, doxorubicin, oridonin,paclitaxel, and vemurafenib. And, while it is contemplated that themethod may be amenable for use with any GHR antagonist (or any of anumber of GHR antagonists), in certain embodiments, the antagonist ofthe growth hormone receptor may be pegvisomant.

Another aspect of the present invention may include a method of treatingcancer in a subject having cancer cells, said cancer cells including atleast one growth hormone receptor, wherein the method includescontrolling an action of the growth hormone receptor, wherein thecontrolling an action of the growth hormone receptor is caused byinhibiting growth hormone action. This inhibition may be effected viathe use of antibodies (such as antibodies directed against the growthhormone receptor, or antibodies directed against growth hormone.

Again, in this aspect of the present invention, (like the previousaspects described above), the subject may be a human in certainembodiments. And, while the aspects of the present invention arecontemplated for treating cancer in general, and many different types ofcancers more specifically, in certain embodiments, the cancer to betreated may be chosen from breast cancer, colorectal cancer, prostatecancer, hepatic cell carcinoma, and melanoma.

In certain embodiments of this aspect of the invention, the inhibitingof the growth hormone action may be caused by antibodies directedagainst growth hormone. And, in certain embodiments, the inhibiting ofthe growth hormone action may be caused by antibodies directed againstgrowth hormone receptor.

Another aspect of the present invention may include a method of treatingcancer in a subject having cancer cells, said cancer cells including atleast one growth hormone receptor, wherein the method includes reducingserum insulin-like growth factor 1 (IGF1) levels below the normal serumIGF1 level of the subject.

In certain embodiments of this aspect, the reducing of serum IGF1 levelsmay be performed by controlling an action of the growth hormonereceptor. And, the controlling an action of the growth hormone receptormay include administering an antagonist of the growth hormone receptor.And, while it is contemplated that the method may be amenable for usewith any GHR antagonist (or any of a number of GHR antagonists), incertain embodiments, the antagonist of the growth hormone receptor maybe pegvisomant.

Another aspect of the present invention may include a method ofmaintaining an anti-tumor drug in cancer cells of a subject bycontrolling an action of at least one growth hormone receptor in thecancer cells. In this aspect of the present invention, the controllingof an action of the growth hormone receptor may include: knock down ofthe growth hormone receptor; co-administration of an antagonist of thegrowth hormone receptor with the anti-tumor drug; inhibiting growthhormone action via antibodies directed against growth hormone; orinhibiting growth hormone action via antibodies directed against thegrowth hormone receptor.

Again, in this aspect of the present invention, (like the previousaspects described above), the subject may be a human in certainembodiments. And, while the aspects of the present invention arecontemplated for treating cancer in general, and many different types ofcancers more specifically, in certain embodiments, the cancer to betreated may be chosen from breast cancer, colorectal cancer, prostatecancer, hepatic cell carcinoma, and melanoma.

Further, as described above, the method of this aspect of the presentinvention may involve (in one embodiment) controlling an action of agrowth hormone receptor via knock down of the growth hormone receptor.In particular embodiments, the knock down of the growth hormone receptormay be performed by siRNA mediated knock down. And, in furtherembodiments, the knock down of the growth hormone receptor may be viaanti-sense RNA directed against the growth hormone receptor. In yetfurther embodiments, the knock down of the growth hormone receptor maybe caused by an antibody specific to the growth hormone receptor.

Further, as described above, this aspect may include (in one embodiment)co-administration of an anti-tumor drug with a GHR antagonist. While itis contemplated that the method may be amenable for use with anyanti-tumor drug (or any of a number of anti-tumor drugs), in certainembodiments, the anti-tumor drug may be chosen from cisplatin,doxorubicin, oridonin, paclitaxel, and vemurafenib. And, while it iscontemplated that the method may be amenable for use with any GHRantagonist (or any of a number of GHR antagonists), in certainembodiments, the antagonist of the growth hormone receptor may bepegvisomant.

Further, and more specifically, one disclosed aspect is a method ofattenuating cancer properties of cells by control of GHR action. Thecells may be any type of cancer cells, such as melanoma cells, forexample. Another aspect is a method of improving a response tochemotherapeutic agents by control of GHR action.

Cancer properties of any cell expressing GHRs may be attenuated inaccordance with this invention. GHRs have been implicated in the growthand function of cancer cells associated with breast cancer, colorectalcancer, prostate cancer, and melanoma, for example. Any cancer thatexhibits increased levels of GHR in the cancer cells may be a target. Abiopsy may be used to determine if such increased levels are present inthe subject.

GHR action may be controlled via administration of GHR antagonists, suchas pegvisomant. Further, GHR action may be controlled via siRNA mediatedGHR-KD or any other means of deactivating or downregulating GHR action.As used herein, the terms “growth hormone receptor knock down” and“GHR-KD” mean decreasing the amount and/or action of the growth hormonereceptor.

In one aspect, the effects of the administration of excess hGH or thedisruption of GH induced signaling on several GH induced intracellularsignaling pathways and downstream proliferative effects in tumor cellgrowth are used to disrupt cancer progression by taking advantage ofGH-GHR interaction. Attenuation of the phosphorylation states ofmultiple intracellular signaling molecules is attainable by the methodsdisclosed, as are differential, yet significant changes in RNA levels ofGH, prolactin, insulin, IGF1, IGF2, and their cognate receptors, whichappear to increase insulin/IGF receptors. Indeed, as used herein GHantagonism may refer not only to a direct action on the GHR but alsoanything that ultimately lowers serum IGF1. The RNA interference(RNAi)-mediated downregulation of GH action in the melanoma cellstranslates into a decrease in cell proliferation, migration, invasion,and colony formation on soft agar assays. GH/GHR action in humanmelanoma cells provides a unique model of GH-regulated multiple criticalcellular processes in the tumor. Further, the dependence of the melanomacells on the GH/GHR interaction validates these interactions aspharmacological targets of intervention in melanoma therapy.

A comprehensive analysis of GH-GHR action in human melanoma cellsexposes a definitive regulation of key intracellular signaling pathways,such as the JAK, STAT (1, 3, and 5), SRC, ERK1/2, AKT, and mTOR, whichmay be critical mediators of early gene activation and drug resistancein melanoma and other forms of cancer. Observed robust GH-dependentmodulation of RNA expressions of hepatocyte growth factor (HGF), theHGF-receptor MET, and Erb-B2 tyrosine receptor kinase 3 (ERBB3) in humanmelanoma cells may indicate a possible involvement of GH on mechanismsof therapy refractoriness in melanoma. Further, melanoma cells mayexpress endogenous GH and the GHR, as well as relatively high levels ofreceptors of the insulin family (IR, IGF1R and IGF2R). The expressionlevels of the insulin and IGF receptor family may be modulated by GHaction, as described herein.

GH putatively occupies a central regulatory role in melanoma cellphysiology and may be involved in the control of multiple mechanisms ofmelanoma growth and progression.

In one aspect, GHR-KD or other downregulation of GHR may be used for thecontrol of four human melanoma cell lines derived from the NCI-60 panelof human cancer cells. The cells were either treated with hGH or hadtheir GHR expression abrogated using GHR-specific siRNA to mimic atransient but acute inhibition of GH action. The subsequent RNA levelsand variations of key components of the GH/IGF axis were then examinedto determine the efficacy of the treatments. Human melanoma cells haveendogenous GH and GHR, with the GH/IGF1 axis affecting expression ofmultiple genes. Signaling networks in the melanoma cell are GH-dependentand were significantly upregulated in presence of GH and also wereseverely suppressed following GHR-KD. GHR-KD in melanoma cellssignificantly suppressed characteristic tumor phenotypes associated withproliferation and metastasis of cancer cells, including melanoma cells.

In another aspect, treatment of melanoma cells with sub-EC₅₀ doses ofanti-cancer drugs, in parallel with blocking GHR action, may result in asignificant suppression of major pathways and processes associated withdrug resistance. This may provide a direct opportunity to reduce thedosage of anti-cancer chemotherapy by several folds while at leastmaintaining an equivalent level of tumor clearance. In turn, theseeffects may allow patients and clinicians to better manage costs andside-effects associated with cancer therapy. The suppression of GHRexpression using siRNA leads to a marked reduction in RNA- and proteinexpression of ATP binding cassette transporters (ABC transporters),significant downregulation of key modulators of the melanogenesispathway, including the microphthalmia-associated transcription factor(MITF) and its target tyrosinase related protein 1 (TYRP1), and asignificant reversal in the RNA and protein levels of markers ofepithelial mesenchymal transition (EMT). Many anti-cancer drugs havebeen approved for a variety of cancers, but certain anti-tumor agentssuch as cisplatin, doxorubicin, paclitaxel, and vemurafenib are usedagainst melanoma, while compounds such as oridonin are under study todetermine possible therapeutic targets. A large hurdle in treatingmelanoma is its intrinsic development of resistance to a given therapyfueled largely by the abundant expression of a repertoire of xenobioticefflux pumps of the ABC transporter family as well as possiblemechanisms of drug sequestration in melanosomes. Following GHR-KD,melanoma cells exhibit significantly longer drug retention and increasedsensitivity to even sub-EC₅₀ doses of anti-cancer drugs. Therefore, GHRreduction or suppression of GH action can be utilized in combinationwith other US Food and Drug Administration (FDA) and European Unionapproved chemo-therapies with established and/or novel anti-tumorcompounds. Thus, an approach of concomitant GHR antagonism or downregulation with conventional therapies may provide improved therapeuticinterventions. This approach may not only lead to a more effectivetreatment plan for a given cancer, but may reduce the required drugdosages. This in turn may lower any physiological side-effects of thedrugs and the associated cost burden.

In another aspect, a method of treating a human patient for cancerincludes controlling the effects of GHR in cancer cells. One manner ofcontrolling the effects of GHR in cancer cells is by administering a GHRantagonist, such as pegvisomant for example. Pegvisomant is arecombinant protein that mimics the interaction of GH with GHR. Ifpegvisomant is administered as a GHR antagonist, dosages may be variedto cause a physiological effect, e.g., a lowering of serum insulin likegrowth factor 1 (IGF 1). For instance, the dosage may be 10 mg, 15 mg,20 mg, 25 mg, 30 mg, 35 mg, 40 mg, 45 mg, 50 mg, 55 mg, 60 mg, 65 mg, 70mg, 75 mg, 80 mg, or even higher. To determine the correct dosage ofpegvisomant, the serum concentrations of IGF 1 may be monitored, withdosage adjusted in 5 mg increments to achieve and maintain normal serumIGF1 levels.

In another aspect, a mechanism for preventing cancer in a human patientis described. The effects of active GHR-induced intracellular signalingmay be reduced or controlled in a prophylactic manner to prevent thegrowth and spread of cancer within the human patient. Such aprophylactic treatment may be indicated, for example, where the patientpresents with polyps and/or other precancerous symptoms.

The following examples may provide further explanation of the describedsubject matter.

EXAMPLES Example 1

In this Example 1, the inventors demonstrated that (1) GHR expression inmelanoma cells was abrogated by siRNA; (2) GHR-KD suppresses humanmelanoma cell migration, invasion, colony formation, and proliferation;(3) GH-GHR action regulates phosphorylation states of intracellularsignaling intermediates in human melanoma cells; and (4) targeting GHRremodels RNA expression of members of the IGF family of proteins andsuppresses oncogenic receptors on/in human melanoma cells. And so, inthis Example 1, the inventors present mechanistic details of GH-GHRaction in human melanoma cells, and an indication that the GH-GHR paircould be an important marker of metastatic melanoma.

Materials and Methods

Cell Culture and GH Treatment

Human malignant melanoma cell lines (part of NCI-60 panel of humancancer cells)—SK-MEL-5 (#HTB-70), SK-MEL-28 (#HTB-72), MALME-3M(#HTB-64), MDA-MB-435S (#HTB-129), and normal human skin fibroblastcells MALME-3 (#HTB-102) cells—were obtained from American Type CultureCollection (ATCC; Manassas, Va.). SK-MEL-5 and SK-MEL-28 were grown andmaintained in EMEM media (ATCC #30-2003), while MALME-3M and MDA-MB-435Swere grown in IMDM (ATCC #30-2005) and RPMI-1640 (ATCC #302001)respectively, as indicated by ATCC protocols. Complete growth media wassupplemented with 5% fetal bovine serum (FBS; ATCC #30-2020) and 1×antibiotic-antimycotic (Thermo Fisher Scientific #15240). MALME-3 cellswere grown in McCoy's medium (ATCC #30-2007) supplemented with 15% FBSand 1× antibiotic-antimycotic. Cells were grown at 37° C. in 5% CO₂ in ahumidified incubator. Half the media was replaced every 48 hr. No hGHwas present in the media or added externally unless specifically noted.Tissue culture treated sterile T-75 and T25 flasks and 6-, 12-, 24-, and96-well plates (Corning, N.Y.) were used. Trypsinization was performedusing 0.25% Trypsin/0.53 mM EDTA in Hank's balanced salt solution (HBSS)without calcium or magnesium (ATCC #30-2101) for 5 min at 37° C. in 5%CO₂.

For hGH treatment, 16 hours after seeding (or 24 hourspost-transfection), the cells were serum-starved for 2 hours inserum-free growth media, and hGH (phosphate buffered saline was used ascontrol where applicable) was added at the noted concentrations (0-, 5-,50-, and 150 ng/ml). Cells were subsequently incubated for 24 hoursbefore evaluating RNA levels. Recombinant hGH was purchased fromAntibodies Online (#ABIN2017921, Atlanta, Ga.).

Transfection

Transfection was performed using siLentFect lipid reagent (Biorad#170-3360, Hercules, Calif.) following the manufacturer's protocol.Pre-designed siRNA duplexes against human GHR (Origene #SR301794,Rockville, Md.) at different concentrations were evaluated, and 20 nMwas found to be optimum for decreasing the GHR RNA by >85%. Mocktransfections were performed using universal scrambled negative controlsiRNA-duplex (Origene #SR30004). TYE-563-fluorescent labeled siRNAduplex (Origene #SR30002) was used as the transfection control. Cellswere trypsinized, counted using a Countess Automated Cell Counter (LifeTechnologies, Carlsbad, Calif.), and seeded at 25,000-30,000 cells/cm²,the cells being allowed to attach for 16-18 hours. The growth media wasreplaced with fresh antibiotic free complete growth medium just prior totransfection. A pre-incubated mix of 20 nM siRNA duplex (scramble or GHRspecific) and siLentFect reagent at 1:1 molar ratio was added to thecells and incubated at 37° C. in 5% CO₂. Media was changed to completegrowth medium plus antibiotics after 24 hours. RNA levels were analyzed48 hours post-transfection, and protein levels were analyzed at 60 hourspost-transfection.

RNA Extraction and RT-qPCR

RNA extraction was performed using the IBI-Trizol based total RNApurification kit (MidSci #IB47632, St. Louis, Mo.), and reversetranscription was performed using Maxima First Strand cDNA synthesis kit(Thermo Fisher Scientific #K1642, Waltham, Mass.) following themanufacturers' protocols. Real time-quantitative PCR and melt curveanalysis were performed using Maxima SYBR-Green qPCR master mix (ThermoFisher Scientific #K0241) and a T100 thermal cycler (Biorad #1861096,Hercules, Calif.). RNA and DNA concentrations were estimated using aNanodrop2000 (Thermo Fisher Scientific, Waltham, Mass.)spectrophotometer. Primers were obtained from Sigma-Aldrich for thefollowing human genes, with primer efficiency being experimentallyconfirmed: GAPDH, b-Actin, GH1, GHR, GHRHR, SOCS2, IGF1, IGF1R, IGF2,IGF2R, PRL, PRLR, insulin (Ins), IR, IGFBP2, IGFBP3, EGFR, HGF, cMET andERBB3. Each sample represented a pool of two replicates per experiment.Experiments were performed at least three times. Each qPCR forindividual genes and every treatment for every cell type was performedin triplicates.

Protein Extraction

Total protein was collected 60 hours post-transfection. The conditionedgrowth media for each treatment type were collected separately forsubsequent analysis of secreted proteins. Total protein was extractedfrom the cells using RIPA buffer (Sigma-Aldrich #R-0278, St. Louis, Mo.)mixed with 1.5× Halt protease and phosphatase inhibitor cocktail(Thermo-Fisher #78442, Waltham, Mass.), following the manufacturer'sprotocol. Briefly, cells were washed twice with chilled sterile 1×phosphate buffered saline (PBS). Thereafter, chilled RIPA buffer at 1 mlper million cells was added and incubated for 5 min. at 4° C. Then, thecells were rapidly scraped for cell lysis. The cell lysate was clarifiedby centrifuging at 8,000×g for 10 min. at 4° C., and the supernatant wascollected and stored at −80° C. for subsequent use. Each sample was apool of three replicates per experiment and each experiment wasperformed three times.

Protein concentration was estimated in duplicates and two dilutions(1:2, 1:4), using the Bradford reagent (Sigma-Aldrich #B6916) and 1mg/ml bovine serum albumin as standards. Absorbance at 595 nm wasmeasured using Spectramax250 (Molecular Devices, Sunnyvale, Calif.) andSoftmaxPro v4.7.1 software.

Western Blotting (WB)

Briefly, cell lysates were separated by SDS-PAGE and transferred tonitrocellulose membrane by a wet-transfer method at 70 mA over 14 hoursat 4° C. and blocked with 5% non-fat dry milk (NFDM) or 5% bovine serumalbumin (BSA) in 1×TBS-T (Tris buffered saline, pH7.2 with 0.1%Triton-X100) for 12-16 hours at 4° C. with gentle rocking. Membraneswere then incubated with primary antibody (at the specific dilutionscited below) for 12-16 hours at 4° C. with gentle rocking. Membraneswere then washed for 5 min. 3 times with 1×TBS-T and incubated withcorresponding secondary antibodies (at the specific dilutions citedbelow) for 2 hours at 25° C. Membranes were then washed for 5 min. 4times with 1×TBS-T, treated with West Femto Chemiluminiscence detectionreagents (Thermo Fisher Scientific), and the chemiluminiscence signalwas captured using a GelDoc (Biorad) fluorescence reader. Densitometricanalysis of the blots was performed by measured band-intensity from thearea-under-curve using ImageJ software.

Primary antibodies at specific dilutions were used to detect thefollowing human proteins: GH (Rabbit, 1:100, Abcam #ab155276), GHR(Mouse, 1:300, SCBT #137185; Goat, 1:100, R&D Systems #AF1210; Rabbit,1:200, Abcam #ab134078), STAT5 (Rabbit, 1:100, CST #9358S),P(Y694/Y699)-STAT5 (Rabbit, 1:100, ActiveMotif #39617, 39618),P(Y701)-STAT1 (Rabbit, 1:100, CST #7649), P(Y705)-STAT3 (Rabbit, 1:100,CST #9145), STAT3 (Rabbit, 1:200, CST #4904), STAT1 (Rabbit, 1:200, CST#9175), p44/42 MAPK (Erk1/2) (Rabbit, 1:2000, CST #9102S), P-p44/42 MAPK(Erk1/2) (Rabbit, 1:3000, CST #4370P), Akt (Rabbit, 1:2000, CST #4685S),P-Akt (Rabbit, 1:1000, CST #4058S), P-Jak2 (Rabbit, 1:200, GeneTex#61122; Rabbit, 1:100, CST #8082), JAK2 (Mouse, 1:200, Sigma Aldrich#SAB4200483), mTOR (Rabbit, 1:1000, CST #2983), P-mTOR (Ser2448)(Rabbit, 1:2000, CST #5536), P-mTOR (Ser2481) (Rabbit, 1:2000, CST#2974), Raptor (Rabbit, 1:500, CST #2280), Rictor (Rabbit, 1:500, CST#2114), GbL (Rabbit, 1:1000, CST #3274), b-Actin (Goat, 1:3000, SCBT#sc1616), GAPDH (Goat, 1:3000, SCBT #sc20357), P(51524)-BRCA1 (Rabbit,1:500, CST #9009), P(5139)-histone H2A.X (Rabbit, 1:1000, CST #9718),histone H2A.X (Rabbit, 1:1000, CST #2595), Caspase-3 (Rabbit, 1:1000,CST #9665), cleaved (Asp175)-Caspase-3 (Rabbit, 1:1000, CST #9664),P(Y416)-SFK (Rabbit, 1:200, CST #2101), P(Y416)-SRC (Rabbit, 1:200, CST#6943), and SRC (Rabbit, 1:500, AbcaM #47405).

Secondary antibodies used were anti-rabbit HRP-linked IgG (Donkey,1:2000, CST #7074P2), anti-goat HRP-linked IgG (Donkey, 1:1000, SCBT#sc2020), anti-rabbit HRP-linked IgG (Donkey, 1:2000, GE #NA934), andanti-mouse HRP-linked IgG (Rat, 1:1000, Antibodies Online #ABIN1589975).

Immunofluorescence (IF)

Cells were seeded at 10,000 cells/cm² in 8-well chamber slides, andtransfection was performed as described above. Transfection media wasreplaced with antibiotic containing complete growth media after 24hours, and cells were fixed after 36 additional hours (a total of 60hours post-transfection). The cells were washed twice with 1×PBS andfixed with 4% freshly-prepared formaldehyde (pH 6.9) for 15 min. at 25°C. It was also possible to use 100% methanol for fixation. Afterfixation, cells were permeabilized with 0.2% Triton-X100 in 1×PBS for 15min. at 25° C., followed by blocking with 1% BSA for 4 hours at 25° C.Incubation time was 12 hours at 4° C. for primary antibody and 2 hoursat 25° C. for secondary antibody. Finally, the slides were washed fourtimes with 1×PBS, and the sample was mounted with Fluoroshield mountingmedium containing DAPI (Abcam #ab104139, Cambridge, UK) and covered witha 60 mm coverslip. The edges were then sealed with nail-polish, and themounted sample was stored at 4° C. for microscopy. Microscopic imagingwas performed using a Nikon Eclipse E600 compound fluorescent microscopefitted with a Nikon DS-Fi1CC camera (Nikon, Tokyo, Japan) andNIS-Elements BR3.2 imaging software. Sera used were rabbitanti-human-Ki67 monoclonal antibody with AlexaFluor488 tag (Abcam#ab154201, 1:300 dilutions); rabbit anti-human GHR monoclonal antibody(Abcam #ab134078, 1:250 dilution); and rat anti-rabbit secondaryantibody with AlexaFluor488 tag (Life Technologies #R37116, 1:500dilution).

Cell Proliferation Assay

A 1% (w/v) resazurin (Sigma-Aldrich #R7017) solution in 1×PBS was madeand filter-sterilized. The final concentration of resazurin in the assaywas 0.004%. Inside the proliferating cells, mildly fluorescent blueresazurin is reduced to a bright pink fluorescent product calledresorufin (stable for 4 hours), which allows for a quantitative measureof the percentage of proliferating cells. In all cases, cells wereincubated at 37° C. in 5% CO₂ for 45-60 min. for adequate sensitivity ofdetection. Briefly, cells were seeded at 10,000 cells/cm² into 96-wellplates and transfected as described above. The resazurin assay wasperformed 60 hours after transfection (unless specified otherwise) andresorufin absorbance was measured at 570 nm (reference wavelength=600nm) using Spectramax250 (Molecular Devices, Sunnyvale, Calif.) andSoftmaxPro software.

Cell Migration Assay

Cell migration assays are standard methods of estimating the repair andregenerative properties of cells. In this example, the Radius CellMigration Assay design from Cell Biolabs (Cell Biolabs #CBA-125, SanDiego, Calif.) was used, and experiments were performed as per themanufacturer's protocol. In this assay, a 24-well plate containing anontoxic, 0.68 mm biocompatible hydrogel spot is present at the centerof the well, which spot prevents the attachment of cells. siRNA treatedcells were trypsinized 48 hours post-transfection, counted, and seededat 5000 cells/well in a pretreated hydrogel spot-containing 24-wellplate. The hydrogel spot was gently removed after 24 hours incubation at37° C. in 5% CO₂. The cells were allowed to migrate for up to 48 hoursat 37° C. in 5% CO₂. Images were captured every 24 hours using a 4×objective (total magnification 40×) employing an inverted Olympus IX70microscope fitted with a Retiga 1300 camera (QImaging, Surrey, BC).Total uncovered area at the beginning and end of assay were quantitatedusing ImageJ software. Experiments were performed in triplicates.

Cell Invasion Assay

The 96-well 3D spheroid BME cell invasion assay (Trevigen, Gaithersburg,Md.) was used to evaluate the ability of cells to invade surroundingtissue. Tumor spheroids are better representatives of tumors in-vivo,compared to tumor cells in a Boyden chamber, as is used in multipleinvasion assay designs. Briefly, siRNA (scramble or GHR specific)treated melanoma cells were trypsinized 48 hours after transfection,counted, and seeded at 5000 cells/well in a 96-well spheroid formationplate, followed by incubation for 72 hours at 37° C. in 5% CO₂ to allowspheroid formation. Thereafter, the invasion matrix was added, followedby addition of 50 ng/ml hGH-containing culture medium as achemoattractant. The invasive behavior of the cells was monitored every24 hours for up to 72 hours. Images were taken every 24 hours using a 4×objective (total magnification 40×) using an inverted Olympus IX70microscope fitted with a Retiga 1300 camera (QImaging, Surrey, BC).Total pixels at the beginning and end of assay were quantitated usingImageJ software. Experiments were performed in triplicate.

Clonogenicity Assay

Colony formation on soft agar or anchorage independent colonization isconsidered to be a very stringent test for malignant transformation ofcells and a hallmark of cancer. Ability of the tumor cell to developcolonies on soft agar reflects a reduced dependence for extracellulargrowth promoting factors, independence from the control of neighboringcells (like keratinocytes in the case of melanocytes), and infinitecapacity to proliferate. In this example, the CytoSelect 96-well format(Cell Biolabs #CBA-130, San Diego, Calif.) was employed, which formatprovides a timely (one week) and quantitative (fluorometric) readout ofthe total colonies formed. Experiments were performed as per themanufacturer's protocol. Briefly, a 0.6% base agar medium containing1×RPMI-1640 (10% FBS) was prepared and allowed to settle for 30 min. at4° C. siRNA treated cells were trypsinized 48 hours after transfection,counted, and seeded at 5000 cells/well in a 0.4% top agar layer alsocontaining 1×RPMI-1640 (10% FBS), being allowed to settle for 15 min. at4° C. Finally, 100 μl of pre-warmed culture media containing 50 μg/mlhGH was added at the top of the culture and incubated for 7 days at 37°C. in 5% CO₂. The media was then removed, the agar was solubilized, andthe cells were lysed in situ. Total DNA content was measured using theCyQuant GR dye (kit component), and fluorescence was measured at 485(ex)/520 nm (em) using a spectramax M2 fluorescence plate reader(Molecular Devices, Sunnyvale, Calif.) and SoftMax Pro v6.2.1 software.Experiments were performed in quadruplicate.

Statistical Analyses

Parametric and non-parametric statistical analyses for comparing RNAlevels were performed using R software (ver3.0.2). For RT-qPCR analysisof RNA, the levels were first normalized against two reference genes(GAPDH and beta-actin), and the ^(2-ddCt) values were compared byWilcoxon signed rank test for significance. A p-value less than 0.05 wasconsidered as significant. The densitometric analyses, clonogenicity,migration and invasion, and resazurin based assays, were compared by apaired student's T-test, and ANOVA was performed (using GraphPad Prismsoftware) to compare for significance (p<0.05 was consideredsignificant).

Results

GHR expression in melanoma cells was abrogated by siRNA: The four humanmelanoma cells selected for this example (SK-MEL-28 cells, SK-MEL-5cells, MALME-3M cells, and MDA-MB-435 cells) reportedly express GHR andare responsive to exogenous hGH treatment. However, the GHR proteinlevel in these cell lines was not known. The siRNA and concentrationwere carefully selected, as was the transfection efficiency for themelanoma cell lines (see FIGS. 1 and 2A-2C). For purposes of thisexample, the siRNA concentration used was 20 nM. In particular, and asshown in FIG. 1 , SK-MEL-28 cells were plated at 10,000 cells/cm² andtreated with either 20 nM GHR-specific siRNA [siRNA-A (shown in panels 1b, and 2 b; of FIG. 1 ); siRNA-B (shown in panels 1 c and 2 c of FIG. 1); siRNA-C (shown in panels 1 d and 2 d of FIG. 1 )] or scramble-siRNA(shown in panels 1 e and 2 e of FIG. 1 ). Untreated cells were treatedwith only transfection reagent (shown in panels 1 a and 2 a of FIG. 1 ).The cells were photographed in grayscale (top row of FIG. 1 ) and at 630nm (bottom row of FIG. 1 ). A Cy3-siRNA duplex at 10 nM was used as areporter. Red fluorescence in FIG. 1 indicated successful transfection.While not shown in FIG. 1 , identical results to the SK-MEL-28 cellswere also obtained with SK-MEL-5, MALME-3M and MDA-MB-435 cells.

And, to optimize siRNA effect of GHR knock-down (KD) on melanoma cellproliferation (see FIGS. 2A-C), SK-MEL-28 cells (FIG. 2A), MALME-3Mcells (FIG. 2B), and SK-MEL-5 cells (FIG. 2C) were transfected with 20nM of either GHR-siRNA or scramble siRNA for 24 hr., and cellproliferation was checked 60 hr. post-transfection using 0.04% resazurin(as described in the methods) and absorbance was read at 570 nm (600nm=reference wavelength). While not shown in FIGS. 2A-2C, data forMDA-MB-435 cells was obtained showing similar results) [*, p<0.05,Students t-test].

In order to verify and quantify GHR RNA in the cell lines, the RNAcollected 48 hours post-transfection from the cells was subjected toRT-qPCR analysis using primers against GHR coding exons. As shown inFIGS. 3A-3C, the results showed high levels of GHR RNA in all fourmelanoma cells, which levels were inhibited by almost 90% followingGHR-KD [FIG. 3A, which shows almost 90% reduction in mRNA levels wasachieved in all four cell lines. Expressions were normalized againstexpression of beta-actin and GAPDH as reference genes (*, p<0.05,Wilcoxon sign rank test, n=6)].

The amount of GHR protein in these cells was also analyzed. Cell lysatescollected 60 hours post-transfection showed an almost completeinhibition of GHR protein following the siRNA treatment, when comparedto the corresponding scramble-transfected controls (FIG. 3C).Densitometry analyses of the WB confirmed a significant (70%-95%)reduction in GHR protein in the melanoma cells. In order to furthervalidate these results, immunofluorescence staining for GHR on thesecells was performed 60 hours post-transfection. Differential yet highlevels of expression of GHR in the cells was observed, with the GHRprotein increasing in order from SKMEL-5, MDAMB-435, MALME-3M andSKMEL-28. The trend was also seen in the WB from the cell lysates asshown in FIGS. 3A-3C.

Following siRNA mediated GHR-KD a dramatic decrease was observed in theimmunofluorescence levels indicative of GHR protein expression, in allthe four cell lines, compared to the scramble-siRNA (scr-siRNA) treatedcontrols (see FIG. 4 ). In that FIG. 4 , in each of the four boxes, toprow (A) shows melanoma cells transfected with scramble siRNA while thebottom row (B) shows melanoma cells transfected with GHR-siRNA. In eachbox the left column shows cellular DNA stained with DAPI (blue) whilethe right column shows the same cells labeled with AlexaFluor 488(green)-conjugated (goat) secondary antibody to rabbit IgG specific forhGHR. From the average of four pictures per cell, maximum GHR-specificfluorescent signal was in the order ofSKMEL-28>MALME-3M>MDAMB-435>SKMEL-5—a trend also seen in WB analyses.ICC/IF was performed on cells 48 hours after transfection.

GHR-KD suppresses human melanoma cell migration, invasion, colonyformation, and proliferation: The effect of GHR-KD on tumor phenotypes,including proliferation, migration, invasion, and clonogenicity, wasanalyzed. Migration and invasion are parameters in tumor cellinteraction with its microenvironment and cancer metastasis. Variousassays are employed to quantify these parameters. When choosing anappropriate assay, the seven day stability of siRNA mediated knock-downof gene expression following transfection may be a consideration.

To analyze the effects of GHR-KD within a relevant time, a commerciallyavailable 3-dimensional spheroid assay was used to visualize andquantitate the invasion of melanoma spheroids into a basement membraneprotein containing hydrogel matrix with all four cell types. The assayused a three-day observation window starting 48 hours post-transfectionwith scr- or GHR-siRNA. Invasion capacity decreased by a minimum of 28%in MDA-MB-435 cells to as much as 62% in SK-MEL-28 cells followingGHR-KD (see FIG. 5 and panels j-l of FIG. 7 ). More specifically, asshown in FIG. 5 , SK-MEL-28 cells transfected with scramble (scr) (shownin panels a1-a4 of FIG. 5 ) or GHR-siRNA (shown in panels b1-b4 of FIG.5 ) were seeded onto U-bottom 96-well plates at 5000 cells/well andallowed to form a spheroid. A hydrogel invasion matrix was added abovethe spheroid and cells were monitored for up to 72 hr. in presence of 50ng/mL hGH. Total pixels representing structural extensions from thespheroid were calculated using ImageJ software and reflected theinvasive ability of the melanoma cells (as shown in panel c of FIG. 5 ).A significant decrease in spheroid invasion was noted following GHR-KD.And, as shown in panels j-l of FIGS. 7 , MALME-3M cells (FIG. 7 , panelj), MDA-MB-435 cells (FIG. 7 , panel k), and SK-MEL-5 cells (FIG. 7 ,panel 1) transfected with scramble (scr)- or GHR-siRNA were seeded ontoU-bottom 96-well plates at 5000 cells/well and allowed to form aspheroid. A hydrogel invasion matrix was added above the spheroid andcells were monitored for up to 72 hr. in presence of 50 ng/mL hGH. Totalpixels representing structural extensions from the spheroid werecalculated using ImageJ software and reflected the invasive ability ofthe melanoma cells. A significant decrease in spheroid invasion wasnoted following GHR-KD. [*, p<0.05, Students t-test, n=3]

To assay the migratory capacity of the melanoma cell lines, thetransfected cells were allowed to converge on a small circular area inthe center of the culture well for up to 48 hours. The percentage freearea at the end time point was calculated using ImageJ. A 2-foldreduction in migration level of SK-MEL-28 cells occurred followingGHR-KD, while for MALME-3M cells, the difference was 15-fold whencompared against scr-siRNA treated controls (see panels a-d of FIG. 6 ,and panels a-i of FIG. 7 ). More specifically, as shown in FIG. 6 ,SK-MEL-28 cells transfected with scr- (shown in panels b1-b3 of FIG. 6 )or GHR-siRNA (shown in panels c1-c3 of FIG. 6 ) as well asun-transfected controls (shown in panels a1-a3 of FIG. 6 ) were allowedto migrate into a 0.68 mm circular spot at the center of the well, inpresence of 50 ng/mL hGH for up to 48 hr. The percentage free area wascalculated using ImageJ software and reflected the decrease/inhibitionin migration (see panel d of FIG. 6 ). A significant decrease inmigration was noted following GHR-KD. Similar results for migration andinvasion assays with MALME-3M, MDA-MB-435 and SK-MEL-5 cells arepresented in FIGS. 2A-2C. And, as shown in panels a-i of FIG. 7 ,MALME-3M cells (FIG. 7 , panels a-c), MDA-MB-435 cells (FIG. 7 , panelsd-f), and SK-MEL-5 cells (FIG. 7 , panels g-i) transfected with scr- orGHR-siRNA were allowed to migrate into a 0.68 mm circular spot at thecenter of the well, in presence of 50 ng/mL hGH for up to 48 hr. Thepercentage free area was calculated using ImageJ software and reflectedthe decrease/inhibition in migration. A significant decrease inmigration was noted following GHR-KD.

Colony formation on soft agar assay was next examined using ahigh-throughput fluorescent readout. This assay is a widely used methodfor evaluating the malignant transformation of cells. A significantreduction, ranging from 19% (SK-MEL-28) to 28% (SK-MEL-5) in colonyformation following GHR-KD was observed despite the presence of hGH inthe media (see panel e of FIG. 6 —showing SK-MEL-5, SK-MEL-28 andMDA-MB-435 cells transfected with 20 nM scramble or GHR-siRNA allowed toform colonies on soft agar for 7 days in presence of 50 ng/mL hGH; thecells were lysed at the end time point and total DNA was quantifiedusing a fluorescent readout, showing a significant decrease in totalnumber of colonies). No marked increase in melanoma migration, invasion,or clonogenicity was observed upon incubation with excess GH (up to 150ng/ml), although there was a trend towards an increase for each (datanot shown).

The cell proliferation of the four melanoma cell lines in response toincreasing doses (5, 50 and 150 ng/ml) of recombinant hGH was alsoevaluated. A significant difference in cell proliferation was observedat a minimum hGH concentration of 50 ng/ml (serum concentration in media1%). Cell proliferation induced by hGH-excess ranged between 10%(SK-MEL-5) to as much as 248% (MALME-3M) at 50 ng/ml hGH; while at thesupra-physiological levels (150 ng/mL), the increase in proliferationranged from 22% (SK-MEL-5) to more than 300% (MALME-3M) (see FIG. 8A).More specifically, SK-MEL-28 cells (FIG. 8A, panel 1), MALME-3M cells(FIG. 8A, panel 2), MDA-MB-435 cells (FIG. 8A, panel 3), and SK-MEL-5cells (FIG. 8A, panel 4) were treated with increasing doses of hGH for48 hr. and cell proliferation was estimated using a resazurin-basedmetabolic assay. As noted above, a significant increase in cellproliferation was noted at and above 50 ng/mL hGH treatment.

On the other hand, a pronounced drop in proliferation levels in all thecell lines was seen when GHR was knocked down. Melanoma cellproliferation decreased by 24% (MDA-MB-435) to 40% (MALME-3M) in GHR-KDcells, even when no GH was added externally, while the trend remainedsimilar even when 50 ng/ml hGH was present in the media (see FIG. 8B).More specifically, SK-MEL-28 cells (FIG. 8B, panel 1), MALME-3M cells(FIG. 8B, panel 2), MDA-MB-435 cells (FIG. 8B, panel 3), and SK-MEL-5cells (FIG. 8B, panel 4) were transfected with 20 nM scramble orGHR-siRNA for 24 hr. and grown for 48 hr. in presence or absence of 50ng/mL hGH. Cell proliferation was estimated using resazurin-basedmetabolic assay. A significant decrease in cell proliferation was notedfollowing GHR-KD. Averages of at least four independent experimentsperformed in quadruplicate were taken [*, p<0.05, Students t-test]. Theresults may indicate that human melanoma cells utilize GH-GHRinteraction to drive aggressive tumor phenotypes.

Possible intracellular signaling networks under GH control that may beresponsible for translating the GH-GHR interaction to theabove-described phenotypes involving tumor progression were investigatednext.

GH-GHR action regulates phosphorylation states of intracellularsignaling intermediates in human melanoma cells: In order to assess theeffects of GHR-KD on the activation states of GH regulated sharedoncogenic signaling pathways, scr-siRNA or GHR-siRNA transfected humanmelanoma cells, at 60 hours post-transfection, were treated with 50ng/ml hGH for 20 minutes, and phosphorylation levels of intracellularsignaling intermediates were analyzed by WB. Results are describedbelow, and shown in FIGS. 9A-9I, 10A-10L, and 11A-11I. For the resultsdescribed and shown in FIGS. 9A-I, SK-MEL-28 cells, 24 hrpost-transfection with either scramble (scr)-siRNA or GHR-siRNA weretreated for ten mins with GH and lysed as described. WB was performedusing appropriate antibodies. Densitometry analyses of individual blotswas performed using ImageJ software and the ratio of phosphorylated vs.total protein levels against untreated scr-siRNA transfected controls.Overall, excess GH increased while GHR-KD decreased phosphorylationstates. Similar results for MALME-3M, MDA-MB-435 and SK-MEL-5 humanmelanoma cells are presented in FIGS. 10A-10L. [In FIGS. 10A-10L,relative RNA expression was quantified for GH, PRL, IGF1, GHR, PRLR,IGF1R, IGF2R, GHRHR, IGFBP2, IGFBP3 and SOCS2 in MALME-3M melanoma cellsfollowing addition of 0, 5, 50 and 150 ng/mL hGH or following GHR-KD, inpresence or absence of 0 and 50 ng/mL hGH. In all cases, exogenous hGHtreatment was for 24 hr. ERNA levels were normalized against expressionof beta-actin and GAPDH as reference genes. [*, p<0.05, Wilcoxon signrank test, n=4].] Blots from individual experiments were quantified andthe mean of three blots per antibody was taken. Protein levels werenormalized against expression of f3-actin. [*, p<0.05, Students t test,n=3]. And, for the results described and shown in FIGS. 11A-11I, WB wasperformed using appropriate antibodies. Densitometry analyses ofindividual blots was performed using ImageJ software and the ratio ofphosphorylated vs. total protein levels against untreated scr-siRNAtransfected controls. Overall, excess GH increased while GHR-KDdecreased phosphorylation states. Blots from individual experiments werequantified and the mean of three blots per antibody was taken. Proteinlevels were normalized against expression of f3-actin. [*, p<0.05,Students t test, n=3].

As shown in FIGS. 9A-9I and 11A-11I, a dependence of various signalingpathways on the GH-GHR interaction in all four human melanoma cells wasobserved (FIGS. 9A and 11I). Densitometry analyses revealed that GHinduced a robust increase in phosphorylation levels of JAK2 (FIGS. 9B,11A) as well as of SRC (FIGS. 9F, 11E), supporting findings in othercellular lines. In fact, the increases in GH-induced phosphorylation ofJAK2, e.g., 1.7-fold (SK-MEL-5) to 6.1-fold (SK-MEL-28), and SRC, e.g.,1.7 fold (MALME-3M) to 3.5 fold (SK-MEL-28), were found to bedose-dependent (FIGS. 9B, 9F). Even in the presence of 50 ng/ml hGH inthe medium, GHR-KD resulted in as much as 75%-90% lower activation ofJAK2 and SRC than corresponding control, often to below the basalactivation states observed across the four cell lines (FIGS. 9B, 9F).

Continuing to refer to FIGS. 9A-9I and 11A-11I, additional routes of GHinduced signaling situated downstream of JAK2 and SRC were investigated,including GH-induced increases in phosphorylation states of STAT5 (FIGS.9C, 11B), STAT1 (FIGS. 9D, 11C), STAT3 (FIGS. 9E, 11D), as well as ofAKT (FIGS. 9G, 11F), mTOR (FIGS. 9H, 11G), and ERK1/2 (FIGS. 9I, 11H) inall four human melanoma cell lines. STAT5 phosphorylation increased by4.1-fold (SK-MEL-28) to 5.8-fold (MALME-3M) at 50 ng/ml hGH; whileGHR-KD effected an 80%-90% reduction of the same (FIGS. 9, 11B). STAT1and STAT3 phosphorylation levels were upregulated at 50 ng/ml hGH, e.g.,MALME-3M with its 2.2-fold increase in STAT1 phosphorylation level and11.9-fold increase in STAT3 phosphorylation level and SK-MEL-28 with its2.4-fold increase in STAT1 phosphorylation level and 1.9-fold increasein STAT3 phosphorylation level, while GHR-KD suppressed phosphorylationsignificantly across all four cells (FIGS. 9D, 9E, 11C, 11D). Activated(tyrosine phosphorylated) GHR, in presence of 50 ng/ml hGH, was found toincrease AKT and its downstream target, mTOR, phosphorylation levels upto 4-fold and 15-fold respectively in SK-MEL-5 cells, while GHR-KDsuppressed the same by more than 90% in all cases (FIGS. 11F, 11G). TheERK1/2 levels were similarly upregulated by GH in three of four melanomacell lines, with a 5-fold increase in SK-MEL-5 cells (FIG. 11H). GHR-KDalso suppressed ERK1/2 phosphorylation by 80% in human melanoma celllines, even in presence of GH.

These signaling pathways are oncogenic “drivers” or enhancers in severalhuman cancers, including melanoma. Thus, these results, dealing withboth excess GH and GHR depletion, show that the GH-GHR pair andinteraction thereof regulates aggressive tumor phenotypes by exertingcontrol over the activation states of certain oncogenic signalingmediators.

Targeting GHR remodels RNA expression of members of the IGF family ofproteins and suppresses oncogenic receptors on/in human melanoma cells:GH-GHR induced intracellular signaling may be associated with that ofseveral other hormones, including prolactin (PRL), insulin (Ins), IGF-1,and IGF-2, and their respective cognate receptors, PRL receptor (PRLR),insulin receptor (IR), IGF-1 receptor (IGF1R) and IGF-2 receptor(IGF2R). In addition, GH action may be correlated with expression of IGFbinding proteins (IGFBP), e.g., IGFBP-2 and IGFBP-3. GH and PRL belongto the same family of class I cytokines, which possess a few similaractions on tissues. Additionally, human skin may be an extra-pituitarysite where both these cytokines and their cognate receptors (GHR andPRLR) may be expressed. Thus, the endogenous RNA levels of GH, as wellas PRL and PRLR, in human melanoma were also quantified.

And so—referring now to FIGS. 12A-12B, 17A-17C, 18A-18F, 19A-19F, and20A-20F—RT-qPCR analysis of GH-IGF axis in human melanoma cells (FIGS.12A-12B) and RT-qPCR analysis of GH-GHR and PRL-PRLR pairs in humanmelanoma cells (FIGS. 17A-17C) was performed. As shown in FIGS. 12A and12B, and for the results described below, the RT-qPCR analysis was ofRNA extracted from SK-MEL-28 cells following addition of 0, 5, 50 and150 ng/mL hGH or following GHR-KD, in presence or absence of 0 and 50ng/mL hGH. Results are discussed below. And, while not shown in FIGS.12A and 12B, similar results for MALME-3M, MDA-MB-435 and SK-MEL-5 humanmelanoma cells are presented in FIGS. 13A-13L, 17A-17C, 18A-18F,19A-19F, and 20A-20F. In FIGS. 13A-13L, (which shows a comparison ofchanges in RNA level expression of key components of GH/IGF-1 axis inSK-MEL-5 cells), relative RNA expression was quantified for GH, PRL,IGF1, GHR, PRLR, IGF1R, IGF2R, GHRHR, IGFBP2, IGFBP3 and SOCS2 inSK-MEL-5 melanoma cells following addition of 0, 5, 50 and 150 ng/mL hGHor following GHR-KD, in presence or absence of 0 and 50 ng/mL hGH. Inall cases, exogenous hGH treatment was for 24 hr. RNA levels werenormalized against expression of beta-actin and GAPDH as referencegenes. [*, p<0.05, Wilcoxon sign rank test, n=4]. In FIGS. 14A and 14B,(which shows a change in markers of DNA damage following GHR-KD),changes in phosphorylation levels of BRCA1 and histone H2A.X wereevaluated using antibodies recognizing phospho-serine 1524-BRCA1 andphospho-serine 139-H2A.X. The p-H2A.X/H2A.X ratio was specificallycompared as the indicator of relative level of phosphorylation. Thep-BRCA1 values were significantly upregulated following GHR-KD butp-BRCA1/BRCA1 ratio was not evaluated. Cells were grown in presence of50 ng/mL exogenous GH and protein level changes were estimated 60 hr.post-transfection. [*, p<0.05, Students t test, n=3]. In FIG. 15 ,(which shows a change in markers of apoptosis following GHR-KD), changesin protein levels of caspase-3 and cleaved caspase-3 were evaluatedfollowing GHR-KD in the presence of 50 ng/mL hGH. And in FIG. 16 ,(which shows the effect of GHR knock down (KD) on melanoma cellmigration), (1) MALME-3M (panels 1 a-1 d and top graph), (2) MDA-MB-435(panels 2 a-2 d and middle graph), and (3) SK-MEL-5 cells (panels 3 a-3d and bottom graph) transfected with 20 nM scramble (panels a and b inthe photographs) or GHR-siRNA (panels c and d in the photographs) wereallowed to migrate into a circular spot at the center of the well, inpresence of 50 ng/mL hGH for up to 48 hr. The percentage free area atthe end time point was calculated using ImageJ software and reflectedthe decrease/inhibition in migration. A significant decrease inmigration was noted following GHR-KD. [*, p<0.05, Students t-test, n=3].In all cases, exogenous hGH treatment was for 24 hr. RNA levels werenormalized against expression of β-actin and GAPDH as reference genes[*, p<0.05, Wilcoxon sign rank test, n=4]. And, in FIGS. 17A-17C,relative RNA levels of GH, GHR, PRL, and PRLR, following RT-qPCR of RNAextracted from MALME-3M, MDA-MB-435, and SK-MEL-5 cells followingaddition of 0, 5, 50 and 150 ng/mL hGH or following GHR-KD, in presenceor absence of 0 and 50 ng/mL hGH, are shown. Results are discussedbelow. In all cases, exogenous hGH treatment was for 24 hr. RNA levelswere normalized against expression of β-actin and GAPDH as referencegenes. [*, p<0.05, Wilcoxon sign rank test, n=4]

In all four melanoma cells, a relatively high level of GH RNA [panels 1and 2 of FIG. 12A and FIGS. 17A-C] was observed, potentially indicatinga mechanism of intrinsic GH production and the possibility of autocrineaction in these GHR-expressing human melanoma cells. PRL and PRLR weredetectable, but at levels 4-fold and 110-fold lower than GH and GHRlevels, respectively, in SK-MEL-28 cells (FIG. 12A, panel 1). A similarlevel of RNA expression was observed in all four melanoma cell lines. Inthe SK-MEL-28 cells, GHR knockdown resulted in a 1.7-fold rise in GH andPRL (FIGS. 12A, panels 2 and 3), which was closely reflected in othercell lines (FIGS. 17A, panel 3; 17B, panel 1; 17B, panel 3; 17C, panel1). A 6- to 10-fold rise in PRLR levels was found with a concomitant 8-to 10-fold drop in GHR levels in SK-MEL-28 cells (FIGS. 12A, panels 4and 5). This significant rise in PRLR with drop in GHR expression wasseen also in MALME-3M and MDA-MB-435 cells (FIGS. 17A, panel 4, and 17B,panel 4). Without intending to be bound by any particular theory, thisdata-set suggests a compensatory rise in PRL dependency of the melanomacells, in absence of GH action, potentially caused by abrogation of GHRexpression.

IGF1 may be elevated in melanoma patients, relative to non-melanomahuman subjects, and the IGF1-IGF1R system may be involved withautocrine/paracrine regulation of melanoma growth. The network of Ins,IGF1, and IGF2, as well as their cognate receptors (IR, IGF1R, IGF2R)and binding proteins (IGFBPs), may be involved with melanoma diseaseprogression. Thus, the levels of these species were examined followingthe perturbation of the GH-GHR axis by either addition of exogenous hGHor GHR-KD. No IGF2 or insulin RNA expression in the melanoma cell lineswas observed. However, low levels of IGF1 and very high levels (25-foldgreater than GHR) of IGF1R and IGF2R expression were observed (FIG. 12A,panel 1). Insulin receptors (IRs) were also detected at equivalentlevels with GHR (FIG. 12A, panel 1). Although GH-excess did not causeany consistent variation in the levels of the low amounts of IGF1 RNAdetected, GHR-KD resulted in a 2-fold (MDA-MB-435) to 8.6-fold(MALME-3M) increase of IGF1 RNA in the four melanoma cells (panel 1 ofFIG. 12B, and FIGS. 18A, 19A, and 20A). Although excess GH caused noconsistent variation in the RNA levels, a differential pattern ofregulation of the IGF receptors following GHR-KD was observed. InSK-MEL-28 (FIG. 12B) and MALME-3M (FIGS. 18A-18F) cells, GHR-KD resultedin an increase in the level of IGF1R (1.5-fold) and IR (2-fold), as wellas a drop in IGF2R (2-fold). FIGS. 18A-18F show the RT-qPCR analysis ofcomponents of IGF axis in MALME-3M cells. Relative RNA levels of IGF1(FIG. 18A), IGFBP2 (FIG. 18B), IGFBP3 (FIG. 18C), IGF1R (FIG. 18D),IGF2R (FIG. 18E) and IR (FIG. 18F), following RT-qPCR of RNA extractedfrom MALME-3M cells following addition of 0, 5, 50 and 150 ng/mL hGH orfollowing GHR-KD, in presence or absence of 0 and 50 ng/mL hGH. In allcases, exogenous hGH treatment was for 24 hr. RNA levels were normalizedagainst expression of β-actin and GAPDH as reference genes. [*, p<0.05,Wilcoxon sign rank test, n=4]

Without intending to be bound by any particular theory, the net effectof this remodeling of IGF receptor distribution may help explaining thedynamicity in targeting receptor tyrosine kinases in melanoma.IGF-binding proteins 2 (IGFBP2) and 3 (IGFBP3) were expressed atrelatively high levels in SK-MEL-28 (FIG. 12A, panel 1) and may havedifferential roles in melanoma progression. Increasing IGFBP2 level maycorrelate with progression to metastasis and may actively driveproliferation in melanoma. An increase in IGFBP2 RNA levels in SK-MEL-28cells at high GH levels and a significant decrease following GHR-KD(FIG. 12B, panel 2) were observed. This 2-fold (SK-MEL-28) to 4-fold(MALME-3M) decrease in IGFBP2 levels subsequent to GHR-KD was observedin all melanoma cell lines (FIGS. 18B, 19B, and 20B—with FIGS. 19A-19Fshowing RT-qPCR analysis of components of IGF axis in MDA-MB-435 cells,and FIGS. 20A-20F showing RT-qPCR analysis of components of IGF axis inSK-MEL-5 cells).

IGFBP3 may bind IGF1 as well as IGF2 and may have an anti-tumor effectin several types of cancers. Indeed, its concentration decreasesmarkedly in circulation of cancer patients. However, IGFBP3 has alsobeen shown to have an oncogenic potential with drastic increase inexpression in cultured human melanoma cells. With the exception ofSK-MEL-28 cells (FIG. 12B, panel 3), GHR-KD increased IGFBP3 levels byas much as 3-fold (FIGS. 18C, 19C, and 20C). Thus, RNA analysis of IGFaxis in human melanoma, in response to variations in GH action, reflectsan intricate pattern of regulation. The overall change in responsivenessto circulating or paracrine insulin and IGFs, induced by blockade of GHaction is, therefore, of interest.

In the course of studying two spectra of GH action, i.e., GH excess andGHR-KD, on human melanoma cells, significant modulation was observedwith response to changes in GH action in a set of three genes, i.e., theautocrine system of HGF and its cognate receptor MET and the Erb-B2receptor tyrosine kinase 3 (ERBB3 or HER3), believed to be induced by GHin different tissues and to be drivers of aggressive disease progressionand melanoma drug resistance. RT-qPCR analysis of 17 human melanomasamples identified the existence of a tumor driving HGF-MET axis. Tothat end, FIGS. 21A-21D show relative RNA levels of MET, HGF, and ERBB3following RT-qPCR of RNA extracted from SK-MEL-28, MALME-3M, MDA-MB-435,and SK-MEL-5 cells following addition of 0, 5, 50 and 150 ng/mL hGH orfollowing GHR-KD, in presence or absence of 0 and 50 ng/mL hGH. SOCS2was used as an internal control for GH action. Results are discussedbelow and shown in FIGS. 21A-21D. In all cases, exogenous hGH treatmentwas for 24 hr. RNA levels were normalized against expression of β-actinand GAPDH as reference genes. [*, p<0.05, Wilcoxon sign rank test, n=4]

Low levels of HGF and consistently high levels of MET and ERBB3 RNA wereobserved in the four melanoma cell lines (FIG. 12A, panel 1). Both HGFand MET expression levels were significantly upregulated in adose-dependent manner with added GH in SK-MEL-28 (FIGS. 21A, panels 1and 2) and MALME-3M (FIGS. 21B, panels 1 and 2) cells to more than2-fold at maximum GH concentrations. In comparison, this GH-excessmediated increase in expression was more than 50% reduced by GHR-KD inall the four cell lines (see panels 1 and 2 of FIGS. 21A-21D). ERBB3showed a similar upregulation under GH stimulation while GHR-KD caused adrop in its levels (see panel 3 of FIGS. 21A-21D). SOCS2 was used as aninternal control to monitor GHR-KD effects in all RT-qPCR experiments(see panel 4 of FIGS. 21A-21D). Therefore, mechanistic details of GH-GHRactivity in melanoma are provided in this example and this activity isalso validated as therapeutic targets to abrogate melanoma growth andproliferation.

Discussion of the Above Results

Human melanoma continues to be a serious cause of global mortality. Theexample provided above (Example 1) presents mechanistic details ofGH-GHR action in human melanoma cells. Detectable levels of hGH RNA andprotein, as well as its cognate GHR, were observed on human melanomacells. Basal level phosphorylation of GH-regulated intracellularsignaling networks, such as JAK2, STATs 1, 3, 5, ERK1/2, SRC, AKT, andmTOR, in absence of externally added GH, suggested the presence of anautocrine ligand-receptor loop existent and critical in these fourmelanoma cell lines, although there is no intention to be bound by anyparticular theory. This observation indicates that GH-GHR pair could bean important marker of metastatic melanoma.

Without intending to be bound by any particular theory, endocrine aswell as paracrine/autocrine GH appears to directly activate certainintracellular signaling pathways and drive aggressive tumor phenotypesand EMT in human melanoma, as shown above. Further dissecting theautocrine vs. intracrine roles of this ligand-receptor pair using humanmelanoma as a model might be of substantial interest. Skin is anextra-pituitary site of GH as well as PRL expression and autocrineeffect. PRL and expression of PRLR on tumor tissues are implicated inbreast and prostate cancers for a considerable time via its mitogenicand angiogenic properties. Low but consistent RNA levels of both PRL andPRLR were observed in the example above, as was a consistent marked risein PRLR levels following GHR-KD in SK-MEL-28, MALME-3M, and MDA-MB-435cells. The presence of excess GH potentiated the effect. PRL-PRLRsignaling engages intracellular mediators, such as JAK2, PI3K, ERK1/2,and STAT5, which overlaps with GHR signaling pathway.

The siRNA mediated GHR-KD could lead to a compensatory non-canonicalbinding of GH-PRLR and subsequent downstream signaling. Basalphosphorylation of the ERK1/2 and AKT/mTOR components was observed inall four melanoma cell lines. Without intending to be bound by anytheory, a constitutively active RAS, harboring the V600E mutation inthese cell lines, is believed to be the cause of this observation.However, on GHR-KD, a decrease in ERK1/2, AKT, and mTOR was observed inall cases, often below the basal levels, irrespective of presence ofhGH. Without intending to be bound by any particular theory, thissignificant downregulation may indicate that suppression of an activeautocrine GH-GHR interaction contributes significantly to downregulation of the basal phosphorylation states of these signalingpathways. The residual phosphorylation observed following GHR-KD,although significantly low, could be induced by GH binding andactivation of PRLR as well as other shared signaling pathways.Importantly, exogenous GH and GHR-KD had significant enhancing andsuppressing effects respectively, on relevant intracellular signalingpathways. Similarly, the effect of increased PRLR from endocrine orparacrine PRL is of continued interest. However, observed RNA levels ofPRLR in these melanoma cells were more than 100-fold lower than theobserved GHR RNA levels, and no significant variation was observed dueto altered autocrine PRL-PRLR level on GHR-KD-induced effects in eitherthe phosphorylation levels of intracellular signaling intermediates orin the tumoral phenotypes of migration, invasion, and proliferation.

The role of IGF axis in human melanoma prompted an analysis of RNAlevels of insulin-IGF axis in human melanoma cells during GH-excess andGHR-KD. No endogenous insulin or IGF2 RNA or protein levels weredetected in any of the four melanoma cells tested, but RT-qPCR studiesrevealed the presence of IGF1 RNA. IGF1 & IGF2 and their cognatereceptors are believed to be important regulators of multiple humancancers, including melanoma. High levels of RNA of the correspondingcognate receptors, i.e., IR, IGF1R, and IGF2R, were observed in all fourmelanoma cells studied in the above example. Significant suppression ofIGF2R on all melanoma cells was observed following GHR-KD, but asignificant rise in IGF1R and IR RNA levels was observed followingGHR-KD, especially when treated with excess GH.

The melanoma cells also appear to be in a state of heightenedinsulin/IGF sensitivity via abundant expression of IR, IGF1R, and IGF2R,as seen in all four melanoma cells in the above example. Increasedlevels of IGFBP3 were observed following GHR-KD for the four cell lines,along with a concomitant increase in IGF1 levels. Without intending tobe bound by any particular theory, it is speculated that this couldpossibly be an IGF1 mediated increase in IGFBP3 levels. However, theregulatory role of IGF axis in human melanoma appears to be limited atthe early stage of disease progression and not in the case of metastaticmalignant melanoma. Additionally, as with PRL and PRLR, the basal RNAlevels of IGF1 were 3-fold lower than GH levels, and the GH inducedchanges in members of the IGF family apparently had no observablevariation on intracellular signaling or tumor phenotypes, as describedabove.

Overall, in most cancer treatments, achieving a therapeutic reduction inendocrine IGF1 levels appears to be favored in halting tumorprogression. Moreover, starvation or diet restriction induces areduction in circulating IGF1 and may preferentially protect normalcells while sensitizing melanoma cells to chemotherapy. Thus, the use ofGHR-antagonists or any therapeutic modality which decreases GH inducedintracellular signaling, including but not limited to siRNAs, antibodiesto GH or the GHR, and inhibitors of JAK, JAK2, STATs, STAT5, SRC, AKTERK1/2, and mTOR, in melanoma therapy.

Targeting GHR elevates insulin and IGF1 receptors, meaning that GHRantagonism, including with concurrent administration of IGF1Rinhibitors, provides a pathway towards melanoma therapy. Reduction intumor cell proliferation can either be caused by a direct decrease inthe levels of GHR, by downstream signaling, or by reducing circulatingIGF1 levels by decreasing hepatic and other cellular IGF1 output.Therefore, the above example predicts a mechanistic rationale ofcombining GHR antagonism with IGF1R inhibition as a logical combinationtreatment in malignant human melanoma.

Also, the example above shows GH regulation of the autocrine hepatocytegrowth factor (HGF) and its cognate receptor MET (or c-MET) on the fourmelanoma cell lines. Although intrinsic RNA levels of HGF were low,there was significant increase when treated with added hGH in SK-MEL-28and MDA-MB-435 cells, as well as a significant downregulation followingGHR-KD. Moreover, high RNA levels of the HGF-receptor MET were observedon all four melanoma cells, which high RNA levels exhibited a dosedependent rise with added hGH. On the other hand, GHR-KD significantlysuppressed the same, even in presence of relatively high levels of hGH.This set of results suggest a possible transcriptional control of METand HGF expression by hGH.

Additionally, the ERBB family members, EGFR, ERBB1, ERBB2, and ERBB3 maydrive several oncogenic processes in melanoma. RNA levels of ERBB3 wereupregulated in response to excess GH in SK-MEL-28 and MDA-MB-435, and aconsistent suppression occurred following GHR-KD. Both MET and EGFR maystrongly activate the SRC signaling pathway. GH may activate EGFR inliver regeneration. Thus, the results provided in Example 1 indicate aregulatory role of GH on expression of HGF, MET, and ERBB3 in humanmelanoma cells. Identifying the underlying mechanisms of transcriptionalregulation and downstream intracellular targets can add value to theextent of dependence of malignant metastatic melanoma on the GH-GHRaxis.

STAT3 activation in melanoma may drive multiple transformations,including EMT, angiogenesis, and inhibition of apoptosis by increasingexpressions of intrinsic oncogenic factors, such as microphthalmiaassociated transcription factor (MITF). STAT3 activation may alsocooperatively induce downstream factors, such as c-fos. RobustGH-mediated STAT3 regulation is of further interest, including inmelanoma, and commends itself to new studies investigating role of GH incellular reprogramming and cancer initiating cells. STAT3 is also aconverging point in signaling networks for multiple different upstreamregulators, e.g. SRC and JAK2, as well as ERBB family members, such asEGF4 and ERBB3. The results obtained in the above example show thepresence of constitutive activation of SRC and STAT1, 3, and 5 proteinsin melanomal tumors. GH-induced activation of STAT proteins was found tobe active in melanoma. A significant decrease of STAT activation wasobserved below basal levels, even in presence of added GH, with GHR-KD,suggesting (i) attenuation of the autocrine GH-mediated activation, aswell as (ii) sensitivity and dependence of the melanoma cells on GH-GHRinteraction and activation of either JAK2 or SRC or both. The presenceof basal phosphorylation of both JAK2 and SRC kinases, as well as theirrespective changes with GHR-KD and/or added exogenous GH, as observed inall cell lines, may indicate that both signaling mediators may be highlyresponsive to GH in melanoma. Upregulation of the basal STAT1phosphorylation levels suggests GH action as an explanation forobservations in recurrent melanoma phenotypes. The STAT5 dependence onGH-GHR induced activation, as noted above, also suggests the role ofGH-GHR action in activating STAT5, which is believed to be an oncogenicdriver in melanoma and believed to protect the cell againstinterferon-based immunotherapies. In melanoma cells, STAT5 acts tomediate resistance to apoptosis and may be activated by both JAK2 andSRC kinases. Thus, without intending to be bound by any particulartheory, the above results indicating significant basal activation ofJAK2, SRC, STATs 1, 3, and 5, in melanoma suggests that these pathwaysmight be under the control of an autocrine GH-GHR system that wasaffected by GHR-KD. Therefore, along with GHR-KD, these can be evaluatedfrom a new perspective as therapeutic targets in future studies.

In general, the above Example 1 suggests that melanoma cells orchestrateincreased proliferation, invasion, and migration directed by GH, and theinteraction of GH with the GHR regulates intracellular signalingpathways and also upregulates oncogenic pathways, such as HGF-MET andERBB3. In summary, this example presents a mechanistic model of GHregulation in human malignant melanoma cells. Without intending to boundby any particular theory, endocrine or paracrine or autocrine GH bindsto abundantly expressed GHR on human melanoma and activates JAK2 as wellas SRC kinases. This activation leads to phosphorylation of STAT1,STAT3, STAT5, ERK1/2, AKT, and mTOR and further promotes invasion,migration, and proliferation for tumor progression. Together theseresults identify novel regulatory roles of GH in one of the mostaggressive and disease-resistant forms of cancer. Using GHR-KD, theresults demonstrate that targeting GHR can be a point of intervention inmelanoma therapeutics and may be useful even in the context of continualoccurrence of chemotherapy resistance. In the following Example 2, thisunique relationship between GHR levels and drug resistance mechanisms inhuman melanoma is investigated.

Example 2

In this Example 2, the inventors demonstrated that (1) GHR knock-downsignificantly suppresses expression of ABC transporter pumps in humanmelanoma cells; (2) GHR knockdown significantly suppresses RNA levels ofmelanogenesis regulators in human melanoma cells; and (3) GHR knock-downsignificantly modulates markers of EMT in human melanoma cells. Theresults of this Example 2 provide data not only in the context of theeffect of GHR-KD on expression of ABC transporters mediating multi-drugresistance in human melanoma, but also identify cell-specific andmultiple drug-specific variations of seven different ABC transporters inmelanoma. The results reveal a specific expression profile of severalABC transporter pumps in melanoma cells following exposure to specificanti-tumor compounds in the context of decreased GHR, and establish anovel role of regulation of GH in multi-drug resistance in melanoma.

Materials and Methods

Cell Culture

Human melanoma cells SK-MEL-5 (#HTB-70), SK-MEL-28 (#HTB-72), MALME-3M(#HTB-64), and MDA-MB-435S (#HTB-129), as well as normal melanocyteST-MEL (ATCC #30-2001), were purchased from American Type CultureCollection (ATCC; Manassas, Va.) and grown in the recommended media with5% fetal bovine serum (FBS; ATCC #302020) and 1× antibiotic-antimycotic(Thermo Fisher Scientific #15240) at 37° C. in 5% CO₂ in a humidifiedincubator. Recombinant human GH (Antibodies Online #ABIN2017921) wasadded to the media at 50 ng/ml.

Drug Treatments

For treatment of melanoma cells, the following five anti-tumor compoundswere obtained from the sources mentioned: cisplatin (Calbiochem #232120,Darmstadt, Germany), doxorubicin (Sigma Aldrich #D-1515, St. Louis,Mo.), oridonin (Sigma-Aldrich #O-9639, St. Louis, Mo.), Paclitaxel(Sigma-Aldrich #C-7191), and vemurafenib/PLX4032 (ApexBio #A-3004,Houston, Tex.). EC₅₀ values were determined for each drug in every cellline, providing the following EC₅₀ ranges for the four melanoma celllines: cisplatin (3-15 μM), doxorubicin (25100 nM), oridonin (2-8 μM),paclitaxel (2-8 nM), and vemurafenib (2-20 nM). In the subsequentexperiments, the following drug concentrations were used unlessspecified otherwise: cisplatin (0.5 μM), doxorubicin (10 nM), oridonin(0.5 μM), paclitaxel (1 nM), vemurafenib (2 nM). Treatments wereperformed for 24 hours starting 48 hours post-transfection with siRNA.

Transfection

Transfection was performed using siLentFect lipid reagent (Biorad#170-3360, Hercules, Calif.) following the manufacturer's protocol.Pre-designed siRNA duplex against human GHR (Origene #SR301794,Rockville, Md.) at 20 nM was used (siRNA-B: AGCUAGAAUUGAGUGUUUAAAGUTC)to decrease GHR transcripts by >80% in all four melanoma cells, while auniversal scrambled siRNA-duplex (Origene #SR30004) was used as acontrol. Cells were seeded at 25,000-30,000 cells/cm², incubatedovernight for complete attachment to substratum, and a pre-incubated mixof 20 nM siRNA duplex (scramble or GHR specific) and siLentFect reagentat 1:1 molar ratio were then added to the cells and incubated at 37° C.in 5% CO₂. Media was changed after 24 hours. RNA levels were analyzed 48hours post transfection while protein levels were analyzed at 60 hourspost-transfection. For drug treatment, drugs at the specifiedconcentrations noted above were added to the cells 48 hourspost-transfection and treated for 24 hours prior to quantitation of RNAexpressions.

RNA Extraction, RT-qPCR, and Protein Extraction

RNA extraction, RT-qPCR, and protein extraction were performed asdescribed in Example 1, above.

Western Blot (WB)

Western-blot was performed following standard laboratory protocol withfew modifications. Briefly, intracellular proteins were separated bySDS-PAGE and transferred onto a PVDF membrane, then blocked with 5%bovine serum albumin (BSA) in 1×TBS-T (Tris buffered saline, pH 7.2 with0.1% Triton-X100) for 12-16 hours at 4° C. Membranes were then incubatedwith primary antibody (at specific dilutions mentioned below) for 12-16hours at 4° C., followed by wash and incubation with correspondingsecondary antibodies (at specific dilutions mentioned below) for 2 hoursat 25° C. Membranes were then washed and treated with WestFemtoChemilumiscence detection reagents (Thermo Fisher Scientific), and thechemiluminescent signal was captured using a GelDoc (Biorad)fluorescence reader. Densitometry analysis of the blots was performedusing ImageJ software.

Primary antibodies were used to detect the following human proteins: GHR(Mouse, 1:300, SCBT #137185; Goat, 1:100, R&D Systems #AF1210; Rabbit,1:200, Abcam #ab134078), Actin (Goat, 1:3000, SCBT #sc1616), GAPDH(Goat, 1:3000, SCBT #sc20357), Vimentin (Rabbit, 1:3000, CST #5741),E-cadherin (Rabbit, 1:1000, CST #3195), N-cadherin (Rabbit, 1:500, CST#13116), Vimentin (Rabbit, 1:3000, CST #5741), ABCG1 (Rabbit, 1:100,Abiocode #R0254), ABCB8 (Rabbit, 1:100, SAB #31025), and ABCB1/MDR1(Mouse, 1:100, SCBT #sc55510). Secondary antibodies used: anti-rabbitHRP-linked IgG (Donkey, 1:2000, CST #7074P2), anti-goat HRP-linked IgG(Donkey, 1:1000, SCBT #sc2020), anti-rabbit HRP-linked IgG (Donkey,1:2000, GE #NA934), and anti-mouse HRP-linked IgG (Rat, 1:1000,Antibodies Online #ABIN1589975).

Immunofluorescence (IF)

Cells were seeded at 10,000 cells/cm² in 8-well chamber slides, andtransfection was performed as described above. The cells were treatedfor 24 hours with 10 nM doxorubicin or 1 nM paclitaxel, 48 hourspost-transfection. Subsequently cells were fixed with 100% methanol,permeabilized with 0.2% Triton-X100 in 1×PBS for 15 min. at 25° C., andblocked with 1% BSA for 4 hours at 25° C. Incubation time was 12 hoursat 4° C. for the primary antibody and 2 hours at 25° C. for thesecondary antibody. Finally, the slides were washed four times with1×PBS, and the sample was mounted with Fluoroshield mounting mediumcontaining DAPI (Abcam #ab104139, Cambridge, UK), covered with a 60 mmcoverslip, the edges of which were sealed with nail-polish. The mountedsample was then stored at 4° C. for microscopy. Microscopic imaging wasperformed using a Nikon Eclipse E600 compound fluorescent microscopefitted with a Nikon DS-Fi1CC camera (Nikon, Tokyo, Japan) andNIS-Elements BR3.2 imaging software. The antibodies used were Rabbitanti-human-Ki67 monoclonal antibody with AlexaFluor488 tag (Abcam#ab154201, 1:300 dilutions); and Goat anti-rabbit secondary antibodywith AlexaFluor488 tag (Life Technologies #R37116, 1:500 dilution).

Cell Proliferation Assay

The cell proliferation assay was performed as described in Example 1,above.

Drug Retention Assay

The presence of multiple drug resistance pumps along the cellularmembrane is key to the resistance against chemotherapy in certain cellssuch as melanoma. ATP-binding cassette (ABC) transporter pumps in theMDR and MRP family are involved in exclusion of xenobiotics from insidethe cells to outside. This reduces the retention time of drugs inside acell and confers decreased sensitivity to the drug-effects. In thisexample, the Vybrant multidrug resistance assay kit (Molecular Probes#V13180, Eugene, Oreg.) was used for the drug retention assay. The assayuses the non-fluorescent calcein acetoxymethylester (calcein-AM) as adrug-mimic and a substrate for the melanoma cell efflux pumps.Calcein-AM is highly lipid soluble and permeates the cell membrane whereit is converted to a fluorescent calcein by the intracellular esterases.In the absence of (or even decreased) activity of the efflux pumps, theintensely fluorescent calcein is retained and can be measured as anindication of drug retention inside the cell. The assay was performed asper the manufacturer's protocol with some modifications.

Briefly, the siRNA treated cells were trypsinized 48 hours aftertransfection, counted, and seeded at 50,000 cells/well in a black, clearbottom Costar 96-well plate (Corning #3603, Corning, N.Y.). Then,calcein-AM was added at a final concentration of 2 μM, and the cellswere incubated at 37° C. for 2 hours. After thorough washing, thefluorescence was measured at 494 (exc)/517 nm (emi) in a spectramax M2fluorescence plate reader (Molecular Devices, Sunnyvale, Calif.) withthe aid of SoftMax Pro v6.2.1 software. Experiments were performed inquadruplicate.

Statistical Analyses

Statistical analyses were performed as described in Example 1, above.

Results

GHR knock-down significantly suppresses expression of ABC transporterpumps in human melanoma cells: Various levels of RNA for seven ABCtransporter pumps were found in the four melanoma cell lines used inthis study. The RNA levels of ABCB8, ABCC1 and ABCC2 were relativelyhigh while ABCB1, ABCB5, ABCG1 and ABCG2 were lower in these melanomacells. The melanoma cells were then treated with sub-EC₅₀ doses ofcisplatin, doxorubicin, oridonin, paclitaxel, and vemurafenib, all ofwhich have been reported and used for their anti-tumor effects ondifferent classes of cancer cells, especially melanoma. The results foreach transporter are presented separately below.

ABCB1: The effect of GHR-KD on ABCB1 expression following drug treatmentin human melanoma cells is shown in FIGS. 22A-22D, based on relative RNAexpression of ABCB1 in SK-MEL-28 (FIG. 22A), MALME-3M (FIG. 22B),MDA-MB-435 (FIG. 22C), and SK-MEL-5 (FIG. 22D) melanoma cells followingscr- or GHR-siRNA mediated knock-down of GHR levels. Experiments wereconducted in presence of 50 ng/mL hGH. In all cases, drug treatment wasfor 24 hr. starting 48 hr. post-transfection. Expressions werenormalized against expression of ACTB and GAPDH as reference genes [*,p<0.05, Wilcoxon sign rank test, n=3]. Significant upregulation of ABCB1RNA levels was observed in response to cisplatin in SK-MEL-28 (FIG. 22A)and MDA-MB-435 (FIG. 22C) cells and in response to oridonin in SK-MEL-28cells (FIG. 22A). Interestingly, the intrinsic RNA level of ABCB1 wassignificantly downregulated following GHR-KD in presence of cisplatinfor all four melanoma cell lines. ABCB1 expression was markedly reducedfollowing GHR-KD also on exposure to doxorubicin (in MDA-MB-435 andSK-MEL-5), oridonin (in MALME-3M and MDA-MB-435), and vemurafenib (inMDA-MB-435) (FIGS. 22A-22D).

ABCB5: The effect of GHR-KD on ABCB5 expression following drug treatmentin human melanoma cells is shown in FIGS. 23A-23D, based on relative RNAexpression of ABCB5 in SK-MEL-28 (FIG. 23A), MALME-3M (FIG. 23B),MDA-MB-435 (FIG. 23C), and SK-MEL-5 (FIG. 23D) melanoma cells followingscr- or GHR-siRNA mediated knock-down of GHR levels. Experiments wereconducted in presence of 50 ng/mL hGH. In all cases, drug treatment wasfor 24 hr. starting 48 hr. post-transfection. Expressions werenormalized against expression of ACTB and GAPDH as reference genes. [*,p<0.05, Wilcoxon sign rank test, n=3]. As can be seen, RNA levels ofABCB5 were significantly upregulated following treatment with cisplatin,doxorubicin, oridonin and paclitaxel in SK-MEL-28 cells (FIG. 23A). Thesame was observed for doxorubicin and oridonin treatment in MDA-MB-435cells (FIG. 23B), indicating a role of ABCB5 in mediating multi-drugresistance specifically in these two cell lines. Also, GHR-KD causedsignificant downregulation of ABCB5 expression compared to scr-siRNAtreated controls, on exposure to cisplatin (in SK-MEL-28), doxorubicin(in MDA-MB-435), oridonin (in SK-MEL-28 and MDA-MB-435), paclitaxel (inSK-MEL-28 and MDA-MB-435) and vemurafenib (in MDA-MB-435) (FIGS.23A-23D). A rise was observed in ABCB5 levels in MALME-3M cellsfollowing GHR-KD in response to oridonin and vemurafenib treatments(FIG. 23B) while GHR-KD significantly decreased even the basalexpression levels of ABCB5 in absence of any drug in MDA-MB-435 cells(FIG. 23C).

ABCB8: The effect of GHR-KD on ABCB8 expression following drug treatmentin human melanoma cells is shown in FIGS. 24A-24D, based on relative RNAexpression of ABCB8 in SK-MEL-28 (FIG. 24A), MALME-3M (FIG. 24B),MDA-MB-435 (FIG. 24C), and SK-MEL-5 (FIG. 24D) melanoma cells followingscr- or GHR-siRNA mediated knock-down of GHR levels. Experiments wereconducted in presence of 50 ng/mL hGH. In all cases, drug treatment wasfor 24 hr. starting 48 hr. post-transfection. RNA expressions werequantified by RT-qPCR and normalized against expression of ACTB andGAPDH as reference genes. [*, p<0.05, Wilcoxon sign rank test, n=3].ABCB8 is known to induce doxorubicin resistance in human melanoma cells,including MDA-MB-435. Consistent with previous observations, significantupregulation of ABCB8 levels was observed following exposure todoxorubicin in MDA-MB-435 (FIG. 24C), MALME-3M (FIG. 24B), and SK-MEL-5(FIG. 24D) cells. A significant upregulation of ABCB8 was also observedon treatment with paclitaxel in MALME-3M (FIG. 24B) and SK-MEL-5 (FIG.24D) cells, while vemurafenib induced a robust increase in ABCB8 inSK-MEL-28 cells (FIG. 24A). When the GHR was knocked down, a strongdownregulation of ABCB8 to below basal levels was observed followingexposure to cisplatin (in SK-MEL-28 and MDA-MB-435), doxorubicin (in allfour cell lines), paclitaxel (in MALME-3M, MDA-MB-435 and SK-MEL-5), andvemurafenib (in SK-MEL-28 and MDA-MB-435) (FIGS. 24A-24D).

ABCC1: The effect of GHR-KD on ABCC1 expression following drug treatmentin human melanoma cells is shown in FIGS. 25A-25D, based on relative RNAexpression of ABCC1 in SK-MEL-28 (FIG. 25A), MALME-3M (FIG. 25B),MDA-MB-435 (FIG. 25C) and SK-MEL-5 (FIG. 25D) melanoma cells followingscr- or GHR-siRNA mediated knock-down of GHR levels. Experiments wereconducted in presence of 50 ng/mL hGH. In all cases, drug treatment wasfor 24 hr. starting 48 hr. post-transfection. Expressions werenormalized against expression of beta-actin and GAPDH as referencegenes. [*, p<0.05, Wilcoxon sign rank test, n=3]. As can be seen, ABCC1levels were particularly upregulated in response to paclitaxel treatmentin SK-MEL-28 and SK-MEL-5 cells (FIGS. 25A and 25D). However, followingGHR-KD significant suppression of ABCC1 RNA levels was observed inresponse to doxorubicin (in MALME-3M), oridonin (in SK-MEL-28 andSK-MEL-5), paclitaxel (in SK-MEL-28, MALME-3M and SK-MEL-5), andvemurafenib (in MDA-MB-435) (FIGS. 25A-25D).

ABCC2: The effect of GHR-KD on ABCC2 expression following drug treatmentin human melanoma cells is shown in FIGS. 26A-26D, based on relative RNAexpression of ABCC2 in SK-MEL-28 (FIG. 26A), MALME-3M (FIG. 26B),MDA-MB-435 (FIG. 26C), and SK-MEL-5 (FIG. 26D) melanoma cells followingscr- or GHR-siRNA mediated knock-down of GHR levels. Experiments wereconducted in presence of 50 ng/mL hGH. In all cases, drug treatment wasfor 24 hr. starting 48 hr. post-transfection. Expressions werenormalized against expression of beta-actin and GAPDH as referencegenes. [*, p<0.05, Wilcoxon sign rank test, n=3] As can be seen,paclitaxel significantly increased RNA levels of ABCC2 transporter inSK-MEL-28 (FIG. 26A), MALME-3M (FIG. 26B), and SK-MEL-5 (FIG. 26D). Thesame effect was observed for vemurafenib in SK-MEL-28 (FIG. 26A) andcisplatin in MDA-MB-435 (FIG. 26C) melanoma cells. GHR-KD resulted in adecrease in ABCC2 levels on exposure to cisplatin (in MDA-MB-435 andSK-MEL-5 cells), doxorubicin (in MDA-MB-435), paclitaxel (in SK-MEL-28and MDA-MB-435), and vemurafenib (SK-MEL-28, MDA-MB-435 and SK-MEL-5cells) (FIGS. 26A-26D).

ABCG1: The effect of GHR-KD on ABCG1 expression following drug treatmentin human melanoma cells is shown in FIGS. 27A-27D, based on relative RNAexpression of ABCG1 in SK-MEL-28 (FIG. 27A), MALME-3M (FIG. 27B),MDA-MB-435 (FIG. 27C), and SK-MEL-5 (FIG. 27D) melanoma cells followingscr- or GHR-siRNA mediated knock-down of GHR levels. Experiments wereconducted in presence of 50 ng/mL hGH. In all cases, drug treatment wasfor 24 hr. starting 48 hr. post-transfection. RNA expressions werequantified by RT-qPCR and normalized against expression of ACTB andGAPDH as reference genes. [*, p<0.05, Wilcoxon sign rank test, n=3]. Inthe four melanoma cell lines tested, ABCG1 was significantly upregulatedconsistently for a number of drugs. ABCG1 levels surged in SK-MEL-28 inresponse to cisplatin, doxorubicin, paclitaxel, and vemurafenibtreatment (FIG. 27A), in MALME-3M cells in response to doxorubicin (FIG.27B), and in MDA-MB-435 cells in response to cisplatin, oridonin andpaclitaxel (FIG. 27C). On the other hand, GHR-KD had an equally drasticeffect in significantly downregulating ABCC2 following exposure tocisplatin (in SK-MEL-28 and MDA-MB-435), doxorubicin (in SK-MEL-28,MALME-3M and MDA-MB-435), oridonin (in SK-MEL-28 and MDA-MB-435),paclitaxel (in SK-Mel-28, MALME-3M and MDA-MB-435), and vemurafenib (inSK-MEL-28 and MDA-MB-435). Only in the case of SK-MEL-5 was a rise inABCG1 levels observed following GHR-KD basally as well as in presence ofall drugs tested (FIG. 27D).

ABCG2: The effect of GHR-KD on ABCG2 expression following drug treatmentin human melanoma cells is shown in FIGS. 28A-28D, based on relative RNAexpression of ABCG2 in SK-MEL-28 (FIG. 28A), MALME-3M (FIG. 28B),MDA-MB-435 (FIG. 28C), and SK-MEL-5 (FIG. 28D) melanoma cells followingscr- or GHR-siRNA mediated knock-down of GHR levels. Experiments wereconducted in presence of 50 ng/mL hGH. In all cases, drug treatment wasfor 24 hr. starting 48 hr. post-transfection. Expressions werenormalized against expression of beta-actin and GAPDH as referencegenes. [*, p<0.05, Wilcoxon sign rank test, n=3]. As can be seen, ABCG2levels were significantly upregulated in SK-MEL-28 cells on exposure todoxorubicin, paclitaxel and vemurafenib (FIG. 28A), while the same wasobserved in MDA-MB-435 cells in response to cisplatin (FIG. 28C) and inSK-MEL-5 cells in response to doxorubicin and oridonin (FIG. 28D). GHRKD caused a significant decrease in ABCG2 levels on exposure tocisplatin (in MDA-MB-435 and SK-MEL-5), doxorubicin (in SK-MEL-28,MALME-3M and SK-MEL-5), paclitaxel (in SK-MEL-28), and vemurafenib (inSK-MEL-28, MALME-3M and SK-MEL-5) (FIGS. 28A-28D). The results of GHR-KDon seven different ABC transporter pumps on all four melanoma cell lineson exposure to cisplatin (0.5 μM), doxorubicin (10 nM), oridonin (0.5μM), paclitaxel (1 nM), and vemurafenib (15 nM) are listed in Table 1.

TABLE 1 List of ABC-transporter pumps with significantly down-regulatedRNA expressions following 24 hr. exposure to anti-tumor compounds inGHR-siRNA transfected melanoma cells compared to corresponding scr-siRNAtransfected controls. Drug Efflux Pumps (expression Cell Line Treatmentlevel change, p < 0.05) SK-MEL-28 Cisplatin ABCB1, ABCB5, ABCB8, ABCG1Doxorubicin ABCB8, ABCC1, ABCG1, ABCG2 Oridonin ABCB5, ABCC1, ABCG1Paclitaxel ABCB5, ABCC1, ABCG1, ABCG2 Vemurafenib ABCB8, ABCC2, ABCG1,ABCG2 MALME-3M Cisplatin ABCB1 Doxorubicin ABCB8, ABCC1, ABCG1, ABCG2Oridonin ABCB1, ABCB5, ABCG1 Paclitaxel ABCB8, ABCC1, ABCG1 VemurafenibABCB5, ABCG2 MDA-MB-435 Cisplatin ABCB1, ABCB8, ABCC2, ABCG1, ABCG2Doxorubicin ABCB1, ABCB5, ABCC2, ABCG1 Oridonin ABCB1, ABCB5, ABCG1Paclitaxel ABCB5, ABCB8, ABCG1, ABCG2 Vemurafenib ABCB1, ABCB5, ABCB8,ABCC1, ABCG1 ABCC2, SK-MEL-5 Cisplatin ABCB1, ABCC1, ABCC2, ABCG2Doxorubicin ABCB1, ABCB8, ABCG2 Oridonin ABCC1 Paclitaxel ABCB8, ABCC1,ABCC2 Vemurafenib ABCC2, ABCG2

FIGS. 29A-29C then show the change in ABC transporter pumps followingGHR-KD. To show this, changes in protein expressions of ABCG1 and ABCB8were analyzed. Western blot comparison was done for protein extractedfrom all four melanoma cells, 60 hr. post-transfection with GHR- orscr-siRNA. Blots were quantified using ImageJ software and mean of threeblots per sample was taken. Expressions were normalized againstexpression of ACTB (β-actin). [*, p<0.05, Students t test, n=3]. This WBanalysis showed significantly lower ABCC1 levels in SK-MEL-28, MALME-3Mand MDA-MB-435, (FIGS. 29A and 29C), while protein levels of ABCB8 werefound to significantly lower in GHR-KD samples of MALME-3M, MDA-MB-435and SK-MEL-5 cells (FIGS. 29B and 29C). These results are consistentwith the levels of RNA expression observed herein.

It was noted in the Example 1 that externally added GH did not produce amarked or consistent effect on the aggressive tumor phenotypes inmelanoma. Without intending to be bound by any particular theory, thismay be ascribed to the melanoma cells expressing GH RNA and having anintrinsic (autocrine) ligand-receptor loop wherein the autocrine-GH mayhave a much more pronounced effect than exogenously added GH.Regardless, the effects of 24-hour exposure to added GH (50 ng/ml) onthe ABC-transporter RNA expressions were assessed in presence of theabove-mentioned anti-tumor agents at the specified concentrations.

Referring now to FIGS. 30A-30C and 31A-31C, FIGS. 30A-30C show theeffect of GHR excess on ABCB8, ABCC1, ABCC2 and ABCG2 expressionsfollowing drug treatment in human melanoma cells, and FIGS. 31A-31C showthe effect of GHR excess on ABCB1, ABCB5, and ABCG1 expressionsfollowing drug treatment in human melanoma cells. More specifically,FIGS. 30A-30C shows relative RNA expression of the four most abundantlyexpressed drug transporters of the ABC-family transporters in SK-MEL-28(FIG. 30A), MALME-3M (FIG. 30B), and SK-MEL-5 (FIG. 30C) melanoma cellsfollowing 24-hour exposure to different anti-cancer drugs in absence orpresence of 50 ng/mL GH was done. (Cis=cisplatin, dox=doxorubicin,ori=oridonin, pac=paclitaxel, vem=vemurafenib). Expressions werenormalized against expression of beta-actin and GAPDH as referencegenes. [*, p<0.05, Wilcoxon sign rank test, n=3]. And FIGS. 31A-31C morespecifically shows relative RNA expression of the ABC-family of drugtransporters in SK-MEL-28 (FIG. 31A), MALME-3M (FIG. 31B), and SK-MEL-5(FIG. 31C) melanoma cells following 24-hour exposure to differentanti-cancer drugs in absence or presence of 50 ng/mL GH was done.(Cis=cisplatin, dox=doxorubicin, ori=oridonin, pac=paclitaxel,vem=vemurafenib). Expressions were normalized against expression ofbeta-actin and GAPDH as reference genes. [*, p<0.05, Wilcoxon sign ranktest, n=3]. As can be seen from the figures, SK-MEL-28 cells showed anupregulation in ABCB8 (in response to Doxorubicin and vemurafenib) (FIG.30A, panel 1), ABCC1 (in response to vemurafenib) (FIG. 30A, panel 2),ABCG2 (in response to oridonin and paclitaxel) (FIG. 30A, panel 4), andABCB1 (in response to doxorubicin and vemurafenib) (FIG. 31A, panel 1)in presence of GH. MALME-3M cells showed a similar increase in ABCB8 (inresponse to cisplatin) (FIG. 30B, panel 1), ABCC2 (in response todoxorubicin) (FIG. 30B, panel 3), ABCB1 (in response to oridonin) (FIG.31B, panel 1), and ABCG1 (in response to doxorubicin) (FIG. 31B, panel3). In SK-MEL-5 melanoma cells too, excess GH also caused an increase ofABCB8 (in response to cisplatin and vemurafenib) (FIG. 30C, panel 1),ABCC2 (in response to oridonin) (FIG. 30C, panel 3), ABCG2 (in responseto cisplatin, oridonin and vemurafenib) (FIG. 30C, panel 4), and ABCB5(in response to cisplatin, doxorubicin, oridonin, paclitaxel andvemurafenib) (FIG. 31C, panel 2). The presence of GH also causeddownregulation of some ABC-transporters (FIGS. 30A-30C and 31A-31C).However, the level of decrease was ˜2-fold and not consistently observedto increase on GHR-KD.

GHR knock-down significantly suppresses RNA levels of melanogenesisregulators in human melanoma cells: The RNA levels of two key componentsof the melanogenesis pathway—MITF and TYRP1—with modulation of theGH/GHR levels were investigated. Referring to FIGS. 32A-32H, relativeRNA expression was quantified for MITF (FIGS. 32A, C, E, and G) andTYRP1 (FIGS. 32B, D, F, and H) in SK-MEL-28 (FIGS. 32A-32B), MALME-3M(FIGS. 32C-32D), MDA-MB-435 (FIGS. 32E-32F) and SK-MEL-5 (FIGS. 32G-32H)melanoma cells following addition of 0, 5, 50 and 150 ng/mL hGH orfollowing GHR-KD, in presence or absence of 0 and 50 ng/mL hGH. In allcases, exogenous GH treatment was for 24 hr. RNA expressions werequantified by RT-qPCR and normalized against expression of ACTB andGAPDH as reference genes. [*, p<0.05, Wilcoxon sign rank test, n=4]. Arobust downregulation of MITF expression was observed in all four GHR-KDmelanoma cells relative to the scramble siRNA-treated controls,irrespective of added GH (FIGS. 32A, 32C, 32E, and 32G). SK-MEL-28 cellsalso exhibited a GH dose dependent increase in RNA levels of MITF (FIG.32A). A GH dose-dependent increase in RNA levels was also observed forthe MITF target TYRP1 in SK-MEL-28 (FIG. 32B), as well as in MALME-3Mcells (FIG. 32D). Additionally, reduced GHR expression correlated with asignificant decrease in TYRP1 levels in all four melanoma cell lines(FIGS. 32B, 32D, 32F, and 32H).

GHR knock-down significantly modulates markers of EMT in human melanomacells: Referring now to FIGS. 33A-33L and 34A-34D, the changes inimportant markers of epithelial mesenchymal transition (EMT) in melanomacells, following a modulation in the GH-GHR axis, were investigated. Asshown in FIGS. 33A-33L, relative RNA expression was quantified forN-Cadherin, E-Cadherin, and vimentin in SK-MEL-28, MALME-3M, MDA-MB-435and SK-MEL-5 melanoma cells following addition of 0, 5, 50 and 150 ng/mLhGH or following GHR-KD, in presence or absence of 0 and 50 ng/mL hGH.In all cases, exogenous hGH treatment was for 24 hr. RNA expressionswere quantified by RT-qPCR and normalized against expression of ACTB andGAPDH as reference genes. [*, p<0.05, Wilcoxon sign rank test, n=4].And, as shown in FIGS. 34A-34D, changes in protein expressions ofvimentin (FIG. 34A), E-cadherin (FIG. 34B) and N-cadherin (FIG. 34C)were analyzed. WB comparison (FIG. 34D) was done in all four melanomacells, 60 hr. post-transfection with GHR- or scr-siRNA. Blots werequantified using ImageJ software and mean of three blots per sample wastaken. Expression levels were normalized against expression of ACTB(B-actin). [*, p<0.05, Students t test, n=3].

In those analyses, a significant dose-dependent increase of N-cadherinand vimentin RNA levels was observed with increase of GH (FIGS. 33A and33B) in SK-MEL-28 cells, while the same remained constant for the otherthree cell lines. The epithelial marker E-cadherin RNA levels were lowfor all four cell lines, which levels decreased significantly (FIG. 331) with increasing GH for MDA-MB-435 cells but not for the other celllines. Increased levels of E-cadherin RNA levels were observed followingGHR-KD, which levels are normally found in low levels in the humanmalignant melanoma cells (FIGS. 33A-33L and 34A-34D). A concomitantsignificant decrease was observed in the RNA levels of N-cadherin (FIGS.33A, 33D, 33G, and 33J) and vimentin (FIGS. 33B, 33E, 33H, and 33K) withGHR-KD consistently in all four melanoma cell lines in this example.Western blot analysis showed results consistent with the RNA levelvariations of E-cadherin, N-cadherin and vimentin following GHR-KD(FIGS. 34A, 34B, and 34C). This is the first report on the variations ofEMT markers under decreased GHR or increased GH levels in human melanomacells.

GHR knock-down leads to significantly higher drug retention anddramatically suppresses cell proliferation in response to sub-EC₅₀ dosesof chemotherapy in human melanoma cells: A significant suppression ofexpression of several efflux pumps, as observed herein, should translateinto a longer retention of xenobiotic (chemotherapeutic) compoundsinside the GHR-KD melanoma cells relative to the scramble siRNA-treatedcontrols. To determine this, and referring now to FIGS. 35A-35D, changesin amounts of calcein retained inside cells following treatment withcalcein-AM ester was analyzed by the fluorescence readout fromintracellular calcein. Increased abundance of transporter pumps isreflected by decreased levels of intracellular calcein. In the reportedfluorometric calcein retention assay, which is sensitive to ABCB1 andABCC1 mediated drug efflux activity, a significantly lower concentrationof retained calcein was observed in the human melanoma cells compared tomelanocytes (FIG. 35A). Following GHR-KD, significantly higherconcentration of calcein was retained inside GHR-siRNA transfectedmelanoma cells relative to the scramble siRNA transfected controls (FIG.35B). The result corroborated the above observations demonstrating theimportance of the GH-GHR interaction in multi-drug resistance inmelanoma. More specifically, in FIG. 35A, there was significantly lowercalcein retention in human melanoma cells compared to human melanocyteST-MEL; and in FIG. 35B, human melanoma cells exhibit significantlyhigher levels of intracellular calcein following GHR-KD. Assays wereperformed 48 hr. post-transfection with either scr-siRNA or GHR-siRNA.Effect of GHR-KD on cell proliferation following 24 hr. exposure to EC₅₀levels of cisplatin and paclitaxel was tested. SK-MEL-28 (FIG. 35C) andMALME-3M (FIG. 35D) cells were exposed to DMSO (vehicle), or 10 umcisplatin (Cis), or 5 nM paclitaxel (Pac) for 24 hr. Treatments weredone 48 hr. post-transfection with either scr-siRNA (scr) or GHR-siRNA(GHR). Mean of three independent experiments performed in triplicate wastaken. [*, p<0.05, Students t test, n=3]

In order to evaluate the effects of decreased levels of drug effluxpumps and significantly higher drug retention times in GHR-KD melanomacells, an immunofluorescence analysis was performed of the expression ofKi-67, an abundantly expressed marker of cell proliferation routinelyused to observe changes in cell viability, including cancer cellviability. The Ki-67 fluorescence levels in GHR-KD were compared tothose of scramble siRNA treated melanoma cells, following a 24 hourtreatment with cisplatin (0.5 μM), doxorubicin (10 nM), oridonin (0.5μM), paclitaxel (1 nM), and vemurafenib (2 nM). More specifically, andreferring now to FIG. 36 , the effect of drug treatment on level ofKi-67-cell proliferation marker in SK-MEL-28 cells following GHR-KD anddrug treatment is shown. SK-MEL-28 cells were exposed to DMSO (FIG. 36pictures designated with letter a), 0.5 um cisplatin (FIG. 36 picturesdesignated with letter b), 10 nM doxorubicin (FIG. 36 picturesdesignated with letter c), 0.5 μM oridonin (FIG. 36 pictures designatedwith letter d), 1 nM paclitaxel (FIG. 36 pictures designated with lettere) or 15 nM vemurafenib (FIG. 36 pictures designated with letter f) for24 hr. Treatments were done 48 hr. post-transfection with eitherscr-siRNA (panels 1 and 2 of FIG. 36 ) or GHR-siRNA (panels 3 and 4 ofFIG. 36 ). Panels 1 and 3 show cellular DNA stained with DAPI whilepanels 2 and 4 show fluorescence signals from AF488-tagged anti-Ki67antibody. In FIG. 36 , picture was taken at 40× magnification; and scalebar represents 500 μm. A dramatic decrease in Ki-67 markers was observedacross all four melanoma cells following GHR KD at dosages 2-10-foldlower than the EC₅₀ doses of the drugs. SK-MEL-28 cells showedparticularly consistent decrease in Ki-67 levels following GHR KD whenexposed to sub-EC₅₀ levels of cisplatin and vemurafenib (FIG. 36 ).

Similar analyses were performed on MALME-3M cells (shown in FIG. 37 ),MDA-MB-435 cells (shown in FIG. 38 ), and SK-MEL-5 cells (shown in FIG.39 ). MALME-3M cells showed the most drastic and consistent decrease inKi-67 levels following GHR-KD when exposed to all five anti-tumorcompounds tested (FIG. 37 ). Similar reduction in cell proliferation wasobserved in MDA-MB-435 cells on exposure to cisplatin (FIG. 38 ). FIG.39 shows results in SK-MEL-5 cells, as well. When the cell proliferationlevels of SK-MEL-28 and MALME-3M cells were quantified followingexposure to EC₅₀ levels of cisplatin (10 μM) and paclitaxel (5 nM), withand without siRNA mediated KD of GHR, drastic inhibition (>90%) wasobserved in all cases (FIGS. 35C and 35D). The results emphasized a netresult of sensitization of the human melanoma cells to low doses ofanti-cancer drugs following GHR-KD.

Discussion of Above Results

The ABC transporter pumps are ATP dependent xenobiotic efflux pumpswhich are employed by various cancer cells as an important mechanism oflowering the intracellular accumulation of cytotoxic anti-cancer drugs.Melanoma expresses a number of ABC efflux pumps, the RNA levels of whichwere specifically investigated for ABCB1, ABCB5, ABCB8, ABCC1, ABCC2,ABCG1, and ABCG2 based on reports of their presence and drug-resistanceactivity in human melanoma. The results of the investigation of ABCtransporters reported above and compiled in Table 1 provides data notonly in the context of the effect of GHR-KD on expression of ABCtransporters mediating multi-drug resistance in human melanoma, but alsoidentifies cell-specific and multiple drug-specific variations of sevendifferent ABC transporters in melanoma. The results reveal a specificexpression profile of several ABC transporter pumps in melanoma cellsfollowing exposure to specific anti-tumor compounds in the context ofdecreased GHR, and establish a novel role and regulation of GH inmulti-drug resistance in melanoma.

Recent studies in GHR knock-out (GHRKO) mice identified decreased levelsof melanocyte stimulating hormone (MSH) compared to their wild-typelittermates. Since MSH is a potent regulator of melanogenesis inmelanocytes as well as melanoma, it is reasonable to speculate aGH-dependent variation in melanogenesis in these cells. To that end, thelevels of two key regulators of melanogenesis, i.e. tyrosinase relatedprotein 1 (TYRP1) and its transcriptional regulator the microphthalmiaassociated transcription factor (MITF), were investigated. TYRP1 is arate limiting enzyme in melanin synthesis pathway. A potentdownregulation of the phosphorylation states of ERK1/2 and AKT/mTORpathways with GHR-KD has been observed, as has a dose-dependent increasewith additional GH. See Example 1, above. This is especially relevantwith respect to MITF regulation, following reports of an ERK1/2 bindingdomain in the MITF gene. MITF is the principal driver of melanocytedifferentiation and development from neural crest cells and occupies acentral role as a driver of melanoma to metastasis as well as in theinteraction of melanoma with its microenvironment. Therefore,identification of a GH-regulation of MITF could be of substantialimportance. The finding of upregulation of MITF and TYRP1 levels withincreasing exogenous GH, as well as marked downregulation of the samefollowing GHR-KD, strongly implicates GH action in control of themelanogenesis pathway used in the melanoma cell lines for activesequestration of drugs via ABC transporters present on the cell membraneand the melanosomal boundary.

EMT plays a physiological role in wound-healing, fibrosis, and in theprogression of cancer. Melanomas break free from the homeostatic controlof keratinocytes by loss in expression of E-cadherin, upregulation ofexpression of fibroblast interacting cadherins such as N-cadherin, andupregulation of mesenchymal markers such as vimentin. Numerous studieshave reviewed the importance of EMT in cancer metastasis. EMT is aregulator of drug resistance in lung cancer. Also, activation of themiRNA-96-182-183 cluster may cause an autocrine GH mediated directregulation of EMT. The above observations of reappearance or increase ofepithelial markers (E-cadherin) and concomitant downregulation ofmesenchymal markers, such as N-cadherin and vimentin, following GHR-KD,at both RNA and protein levels thus describe a role of GH as a regulatorof EMT and the aggressive phenotypes of melanoma multi-drug resistanceand metastasis.

Melanomas have the unique property of resisting drug action by multipleprocesses involving active drug efflux, increased melanogenesis, andconcomitant packaging away of drugs in melanosomes, as well asupregulation of the epithelial-mesenchymal-transition markers as meansof decreased keratinocyte control and increased fibroblast interaction.Melanomas were also found to express one of the highest levels of GHRexpression among all human cancers in the NCI's panel of human cancercell lines. These two unique properties of human melanoma wereinvestigated, and distinct regressive effects of GHR KD on criticalaspects of all the above drug-evading processes were observed.Significant reduction in expression of multiple different ABCtransporter pumps following a decrease in GHR indicates a GH actiondependent mechanism regulating drug efflux from melanoma. In fact, theexistence of GH-GHR mediated regulation of the mTOR pathway in melanomacells is shown in Example 1, above, and GH induced activation of thepathway is known to be necessary for rapid activation of proteinsynthesis, as might be expected to be required in case of expression oftransporter pumps in response to exposure to drugs. These observationsmay be experimentally confirmed in vivo using appropriately designedmouse models of growth hormone transgenic (bGH) or GHR deficient(GHR^(−/−)) mice. Further, the detailed effects of GHR on induction ofapoptotic and/or necrotic cell death, as well as DNA damage, can addsignificant value to our results.

Described above is a mechanistic model of GH action in mediatingmulti-drug resistance in human melanoma through possible transcriptionalregulation of expression of multiple mediators. Indeed, a significantGH-dependent variation in transcription and protein expression ofseveral intracellular mediators of oncogenic signaling pathways inmelanoma was observed (See Example 1), and this observation adds unknowninformation of the downstream effects of the earlier findings.

Decreased drug efflux machinery, increased drug retention, a reversal inEMT markers and a reduced cell proliferation at low doses ofchemotherapy following GHR-KD supports the idea of approaching GH-GHRinteraction as a suitable chemotherapeutic target of intervention as acombination therapy for several classes of anti-tumor compounds. Thus,this approach may have several downstream effects in cancer therapy.First, a lower drug dose applied in combination or followingpretreatment with GHR antagonists can potentially lower the dose andduration of chemotherapy. This, in effect, may reduce the harshside-effects associated with chemotherapy. Second, employing GHRinhibition as a means of sensitizing the tumor cells to otherchemotherapeutic compounds may be one approach in the area of drugdevelopment. Third, a combination of GHR inhibition and chemotherapy cannot only improve the efficacy of available anti-melanoma drugs but canalso assist the development of candidate compounds under development.Decreased drug retention in tumors is a hurdle in establishing efficacyof thousands of good drug candidates in pharmaceutical research anddevelopment. The above Examples directly indicate a breakthrough in thisproblem by establishing that GH-GHR interaction is a mediator ofdrug-resistance and that targeting the same can successfully lead toimproved drug action.

Example 3

In the above Examples 1 and 2, the role of the GH-GHR axis in humanmelanoma cells, using extensive in vitro studies, was described. Theinventors have described a detailed mechanism of GH-dependence of humanmelanoma cells for eliciting resistance to the effects of chemo- andtargeted therapies. In this Example 3, two additional sets of resultsare presented, which further support the inventors' concept ofattenuation of GHR activation in human cancers like melanoma toefficiently counteract their therapy refractoriness.

In the first set, the in vivo effect of high levels of GH on xenograftedmelanoma tumor in syngeneic mice with supra-physiological levels ofcirculating GH is presented. For this purpose, a syngeneic mousemelanoma model was used—B16F10 mouse melanoma cells (that express GHRbut not GH) xenografted in either of two C57BL/6J mouse strains, withaltered GH/GHR axis—transgenic bGH expressing mice (bGH) or GHRknock-out mice (GHRKO)—both with high circulating GH levels. The RNA andprotein expression levels of multidrug efflux pumps of ABC-transporterfamily and known markers of EMT, in the xenografted tumors in bGH orGHRKO mice, were analyzed and compared against xenografts incorresponding wild-type littermate controls.

In the second set, the inventors performed in vitro analyses of GHinduced transcription level changes (mRNA) in the mediators of drugefflux and EMT in two highly drug-resistant and GHR-expressing humancancers—hepatocellular carcinoma (HCC/liver cancer) and melanoma. Veryrecently, others have described a role of autocrine GH in promotingcancer stem cell properties in human liver cancer cells [Chen Y-J, YouM-L, Chong Q-Y, Pandey V, Zhuang Q-S, Liu D-X, Ma L, Zhu T, Lobie P.Autocrine Human Growth Hormone Promotes Invasive and Cancer StemCell-Like Behavior of Hepatocellular Carcinoma Cells by STAT3 DependentInhibition of CLAUDIN-1 Expression. Int J Mol Sci [Internet]. 2017; 18:1274. doi: 10.3390/ijms18061274.]. The inventors in vitro results hereindependently demonstrate the existence of a robust autocrine GH-GHRaxis in human melanoma and HCC cells, markedly upregulated followingdrug exposure, which in turn drives drug efflux and EMT in these cancercells.

Materials and Methods

Cell Culture

SK-MEL-28, SK-MEL-5, Hep-G2, SK-HEP-1, PANC-1, H1299, and MCF7 cellswere purchased from American Type Culture Association (ATCC). SK-MEL-5,SK-MEL-28, SK-HEP-1, Hep-G2, and MCF7 cells were maintained in EMEMmedia (ATCC); PANC-1 was maintained in DMEM (ATCC); H1299 was maintainedin RPMI1640 media. Complete growth medium was supplemented with 10%fetal bovine serum (RMBIO) and 1× antibiotic-antimycotic.

Mouse cDNA

The cDNA from xenografted mouse melanoma tumor B16F10 in GHRKO and bGHmale and female mice, was a kind gift from Dr. Yanrong Qian. Briefly,B16F10 mouse melanoma cells, with abundant expression of GHR, wasinjected subcutaneously into C57BL/6J mice with altered growth hormoneaxis. This constituted a classical syngeneic mouse model of melanomawith dysregulated GH axis. Tumors could grow for 21 days at the end ofwhich the mice were sacrificed and tumors were collected.

RNA Extraction and RT-qPCR

Following treatments, cells were lysed, and RNA extraction was performedusing IBI Tri-isolate kit (IBI), following manufacturer's protocol.RT-qPCR was performed as described previously.

Protein Extraction and Western-Blot

Following treatments, cells were lysed by mild sonication in Ripa lysisbuffer as described previously. SDS-PAGE and western-blot was performedusing general lab-techniques as described previously.

Cell Viability Assay

Cell viability, following treatments, was performed using Invitrogen'sPrestoBlue cell viability assay system. As described previously, it is aresazurin based assay which is reduced to resorufin (absorption at 570nm) by the reducing environment of metabolically viable cells. It wasperformed in a 96-well system as described previously.

Results

GH upregulates ABC-transporter expression in mouse melanoma B16F10 cellsin vitro and in vivo: B16F10 mouse melanoma cells were treated with 50or 500 ng/mL bGH for 6, 24, 48 or 72 hr and the changes in the RNAlevels of specific multidrug exporter pumps were analyzed over time andGH dose. 50 and 500 ng/mL bGH induced a significantly higher RNAexpression of Abcb1, Abcg1 and Abcg2 at 24, 48, and 72 hr (FIGS. 40A-C).The levels of Abcb8, Abcc1, Abcc2, and Abcc4 were not significantlydifferent from untreated controls at any dose or time-point in vitro(data not shown). RNA extracted from B16F10 tumors grown in GHRKO or bGHmice were analyzed for the above ABC-transporters. In bGH mice, thetumor cells and resulting tumors were exposed in vivo to high endogenousGH and high IGF-1; while in GHRKO mice, the tumor cells and resultingtumors were exposed in vivo to high GH but low IGF1. In tumors derivedfrom bGH mice, under basal conditions, i.e., in absence any anti-cancertreatment, the levels of Abcb1, Abcb8, Abcc2, Abcg1, and Abcg2 weresignificantly upregulated compared to tumors in wild-type mice (FIG.34D). In tumors from GHRKO mice, a similar significant upregulation ofAbcb1, Abcb8, Abcg1, and Abcg2 drug transporter RNA levels was observedcompared to the same in wild-type mice (FIG. 40E).

On a closer analysis, a different pattern of GH-induced increase inABC-transporters was seen between male and female mice. Referring now toFIGS. 41A-41D, the figure includes graphs showing genotypic changes inABC efflux pump expressions in B16-F10 mouse melanoma in vivo. Here, RNAlevels in B16F10 mouse melanoma tumors grown in vivo in bGH female (FIG.41A), bGH male (FIG. 41B), GHRKO female (FIG. 41C), and GHRKO male (FIG.41D) mice were queried by RT-qPCR for basal levels of seven differentABC efflux pumps. RNA levels were normalized against expression ofβ-actin and GAPDH as reference genes [*, p<0.05, Wilcoxon sign ranktest]. In the bGH group, female mice had significantly higher levels ofAbcb8, Abcc1, Abcc2, Abcc4 and Abcg2 RNA levels, while male mice hadsignificantly higher levels of Abcb1 and Abcg1, but not the others(FIGS. 41A and 41B). A similar comparison between GHRKO mice revealedthat female GHRKO mice had a significantly higher level of Abcg2 aloneat basal level, while the male GHRKO mice had significantly higher levelof Abcb1, Abcb8, Abcg1, and Abcg2 levels (FIGS. 41C and 41D). Theresults clearly indicate that exposure to supra-physiological levels ofGH markedly upregulates the levels of ABC-type multidrug efflux pumps invitro and in vivo.

GH upregulates expression of markers of EMT in mouse melanoma B16F10cells in vivo: The inventors earlier showed that, in human melanomacells, exogenously added GH upregulates EMT, while attenuating GHRexpression in human melanoma cells, leading to reappearance ofE-cadherin (Cdh1) and downregulation of mesenchymal markers. Therefore,here the inventors queried the basal mRNA levels of known epithelial(Cdh1/E-cadherin) and mesenchymal (Cdh2/N-cadherin, Snai1/Snai1,Vimentin, Zeb1) markers in the tumors of bGH as well as GHRKO micerelative to that seen in control littermates. Referring now to FIGS.42A-42F, that figure includes graphs showing genotypic changes inmarkers of epithelial-to-mesenchymal transition (EMT) in B16-F10 mousemelanoma in vivo. Here, RNA levels in B16F10 mouse melanoma tumors grownin vivo in bGH male (FIG. 42A), bGH female (FIG. 42B), GHRKO male (FIG.42C), and GHRKO female (FIG. 42D) mice were queried by RT-qPCR for basallevels of five known markers of EMT. RNA levels were normalized againstexpression of β-actin and GAPDH as reference genes [*, p<0.05, Wilcoxonsign rank test].

Realtime RT-PCR analyses showed significant upregulation of mRNA levelsof the mesenchymal transcription factors Zeb1 and Snai1 in both bGH andGHRKO mice, with a concomitant marked decrease in Cdh1 mRNA levels(FIGS. 42A-42F). A more detailed analysis revealed that the above trendwas more consistent in both bGH and GHRKO male mice, than in the femalecounterparts (FIGS. 42C-42F). Also, the upregulation in Zeb1 and Snai1levels in GHRKO male mice was suppressed in the female GHRKO mice,although the latter had significantly lower Cdh1 levels than theirwild-type littermates. Further, a significantly lower protein levelexpression of the epithelial marker Cdh1 in female GHRKO mice, and asignificantly higher ABCG2 level in GHRKO male mice compared to thetumors in their wild-type littermates (FIGS. 43A and 43B), was observed.

GH upregulates and GHR-antagonist suppresses the expression ofABC-transporters and markers of EMT in human liver cancer cells invitro: The inventors earlier showed that in human melanoma cellsexpressing GHR, exogenous GH drives the expression of known markers ofEMT, while blocking the GHR expression using siRNA, inhibits GH inducedaction and upregulation in EMT marker expressions. And so, the inventorsperformed a similar experiment with HepG2 and SK-HEP-1 human livercancer cells, which have been extensively studied and known to expressGHR, to verify this observation in human melanoma cells. In vitro, HepG2cells were treated for 3 days with either 50 ng/mL GH (2.5 nM), or 50 nMGHR-antagonist, or both GH and GHR-antagonist, and their RNA expressionswere compared against untreated controls at basal condition (i.e. nodrug treatment). In Hep-G2 cells, exogenous GH treatment was found tosignificantly upregulate the RNA levels of mesenchymal marker vimentin,while downregulating CDH1, the epithelial marker (top panel graph ofFIG. 44 ). On the other hand, treatment with GHR-antagonist alone or inpresence of GH, markedly lowered the levels of mesenchymal markers—SNAIL(SNAI1), ZEB1, SLUG, CDH2, and VIM (top panel graph of FIG. 44 ). Asimilar analysis of ABC-transporter RNA expressions showed thatexogenous GH markedly upregulated levels of ABCC4 and that of thetranscription factor SPI-B, while addition of GHR-antagonist drasticallylowered the basal levels of ABCC4, ABCG1, as well as SPI-B, in HepG2cells (bottom panel graph of FIG. 44 ).

Blocking GHR attenuates the oncogenic HGF-MET loop in human liver cancercells: Hepatocellular carcinoma (HCC) or human liver cancer has one ofthe highest cancer morbidity rates in the world, with only one FDAapproved chemotherapy (sorafenib) available to patients. The hepatocytegrowth factor (HGF) and its cognate receptor (MET), both expressedhighly on different cancers including melanoma, is known to be an activedriver of HCC incidence and progression and have long been implicated asa valuable drug-target [Goyal L, Muzumdar M D, Zhu A X. Targeting theHGF/c-MET Pathway in Hepatocellular Carcinoma. Clin Cancer Res[Internet] 2013; 19: 2310-8. doi: 10.1158/1078-0432.CCR-12-2791; Hu C-T,Wu J-R, Cheng C C, Wu W-S. The Therapeutic Targeting of HGF/c-MetSignaling in Hepatocellular Carcinoma: Alternative Approaches. Cancers(Basel) [Internet] 2017; 9: 58. doi: 10.3390/cancers9060058]. Newgeneration MET-inhibitors like cabozantinib have had partial successagainst human HCC, due to cytotoxic effects at high doses in most recenthuman clinical trials, indicating to unmet needs in counteringdrug-resistance[Kelley R K, Verslype C, Cohn A L, Yang T-S, Su W-C,Burris H, Braiteh F, Vogelzang N, Spira A, Foster P, Lee Y, Van CutsemE. Cabozantinib in hepatocellular carcinoma: results of a phase 2placebo-controlled randomized discontinuation study. Ann Oncol Off J EurSoc Med Oncol [Internet]. Oxford University Press; 2017 [cited 2017 Oct.24]; 28: 528-34. doi: 10.1093/annonc/mdw651].

The inventors had previously shown that knock-down of GHR in turnstrongly attenuates MET as well as HGF transcript levels in humanmelanoma. To verify this observation in another GHR expressing humancancer like HCC, the inventors analyzed the effects of GH andGHR-antagonist treatment on the expression of the oncogenic HGF-MET loopin human liver cancer cells. HepG2 and SK-HEP-1 cells were treated for 3days with either 50 ng/mL GH (2.5 nM), or 50 nM GHR-antagonist, or both,and their RNA expressions were compared against untreated controls atbasal levels (i.e. no drug treatment). No additional effect of added GHon the expression levels of HGF or MET in the liver cancer cell lineswas observed, except a 2-fold increase in MET levels in SK-HEP-1 cells(FIG. 39 ). However, added GHR-antagonist had a drastic effect on theHGF-MET loop in both cell lines. Irrespective of presence of added GH,the antagonist lowered HGF levels by >4-fold in Hep-G2 cells and up to2-fold in SK-HEP-1 cells; while the MET levels were decreased by >2-foldin both Hep-G2 and SK-HEP-1 cells compared to the GH treated samples(FIG. 39 ). This observed nature of the suppressive effect ofGHR-antagonist strongly indicates the existence of a autocrine/paracrineGH action in HCC, as the inventors had found stable GH expression inboth Hep-G2 and SK-HEP-1 cells.

GH-GHR directly activates JAK2, STA5, STAT3, SRC and ERK1/2 pathways inhuman liver cancer cells: To trace the intracellular signaling patternor pathways downstream of GH-GHR interaction in human liver cancercells, the inventors used a time-lapse analysis of the activation statesof known GH-regulated signaling pathways, across time, in Hep-G2 andSK-HEP-1 cells stimulated with 50 ng/mL GH. The inventors observed thatwithin 20 minutes of GH addition in both Hep-G2 and SK-HEP-1 cells, thephosphorylation states of STAT3, STAT5, SRC, and ERK1/2 (p44/42 MAPK)were particularly increased significantly, but not that of p38 MAPK,AKT, mTOR, or S6RP (FIG. 46 ).

Drug-induced autocrine GH-GHR expression drives multiple mechanisms ofdrug resistance in human melanoma cells: The inventors previouslyreported the existence of RNA and protein levels of endogenous GH,beside GHR, in human melanoma cells grown in vitro unlike mouse B16F10cells which express only GHR but no GH. The inventors also reported theexistence of a GH-GHR regulated drug resistance mechanism in humanmelanoma cells. Therefore, the induction of intracellular mechanisms ofdrug resistance following exposure to chemotherapy in melanoma, could belocally turned on by an autocrine/paracrine GH source, in case ofGH-expressing human melanoma cells.

To verify if exposure to chemotherapy alone induces the endogenouslevels of GH or GHR, the inventors treated SK-MEL-28 human melanomacells with 188 nM the chemotherapeutic doxorubicin (=EC₅₀ of doxorubicinagainst SK-MEL-28 cells) and followed the RNA levels of GH and GHRacross 2, 6, 12 and 24-hr following drug addition. The inventorsparallelly analyzed the changes in transcript levels of known markers ofEMT (mesenchymal—SNAI1, CDH2/N-cadherin, VIM;epithelial—CDH1/E-cadherin) and ABC-type multidrug efflux pumps (ABCB1,ABCB8, ABCC1, ABCC2, ABCC4, ABCG1, ABCG2) with time, followingdoxorubicin addition. A consistent increase in autocrine GH transcriptwas observed after 12-hr, with a >2-fold rise by 24-hr, with aconcomitant rise in GHR levels (FIG. 47 ). In synchrony to thisincreased GH response, the transcript levels of CDH2, VIM and SNAI1increased significantly 12-hr after doxorubicin addition, with >2-foldincrease in SNAI1 and >3.5-fold increase in CDH2 at the end of 24 hr(FIG. 47 ). There was a >8-fold reduction in the epithelial markerCDH1/E-cadherin, at the end of 24 hr after doxorubicin addition (FIG. 47). Similarly, following a consistent upregulation of autocrine GH levelsat 12-hr, a 4-fold rise in ABCB1 and an 8-fold rise in ABCG1 (both knowntransporters of doxorubicin in cancer cells) was observed. At the end of24 hr, the RNA levels of ABCB1 and ABCG1 were even higher withsignificantly higher levels of ABCB8, ABCC1 and ABCC4 drug efflux pumpsas well (FIG. 48 ).

Discussion of the Above Results

Previously, the inventors found that knocking down GHR attenuatedABC-type multidrug efflux pump gene expression and EMT in multiple humanmelanoma cell lines. In melanoma, the activation of theepithelial-to-mesenchymal transition (EMT) strongly correlates with atransition to aggressive metastases as well as with upregulation ofmechanisms of drug resistance. Our observation in the syngeneic mousemodel of melanoma was highly consistent with our earlier observation inhuman melanoma cells. A significantly upregulated RNA level of markersof EMT as well as that of ABC drug efflux pumps, even in the absence ofany drug mediated induction, highlight a critical role of GH in possiblyascertaining the intrinsic nature of the tumor. An elegant study byCaramel et al showed how a switch from a Zeb2-dominant phenotype to anEMT-inducing Zeb1-dominant phenotype is a driver of malignancy inmelanoma. Recently Zeb1 was also identified as a critical oncogenicregulator in uveal melanoma. In this study, a marked increase in levelsof Zeb 1 in vivo was observed, under both conditions of elevated GH(both bGH and GHRKO mice). This data along with our observations ofelevated Snai1 and reduced Cdh1 in our syngeneic mouse modeladditionally points to a hitherto unidentified role of GH action indriving phenotypic plasticity of cancer cells. The current studyprovides an excellent support to our earlier in vitro observations ofattenuating ABC-type multidrug efflux pumps by GHR knockdown in humanmelanoma cells. Even in absence of drug treatment, the mRNA levels ofAbcb1a, Abcg1 and Abcg2, which are some of the most studied drugtransporters in cancer, were elevated concomitantly with an elevated GHexposure in bGH and GHRKO mice, relative to that found in their WTlittermates controls. Therefore, melanoma cells on exposure to high GHlevels might remain at an elevated state of resistance. This in turnmight lead to an aggressively drug-resistant phenotype of melanoma.Further, there were some difference between the patterns of alteredexpression of ABC-type multidrug efflux pumps and EMT markers in maleand female mice with elevated GH. The role of estrogen, pattern of GHrelease between male and female mice, and a putative role of adifferential IGF axis could be some potential confounding modulatingfactors in the observation. Overall, the data from the unique syngeneicmouse melanoma model with altered GH levels provide a confirmation ofour previous in vitro observations and bolsters our understanding of theunique regulatory role of GH-GHR pair in specific drug efflux mechanismsin melanoma cells. It provides further insight into the rapidlyunfolding nature of GH regulation of the process of EMT and phenotypeswitches in cancer cells.

Recently, several studies by Peter Lobie's group, indicated apotentially critical role of autocrine GH expression in cancer cells.His group found that human melanoma cells in in vitro express GH, whichis significantly upregulated following drug treatment. Our resultsstrongly support this observation and additionally reveal an intrinsicGH-GHR loop activated within 12 hours of exposure of SK-MEL-28 cells toan anti-cancer drug, which is followed by a marked upregulation of EMTand drug efflux mediators. This is significantly corroborated by ourobserved effects of GHR-antagonist on EMT markers and ABC-transportersin human liver cancer cells which also have endogenous expression of GHas well as GHR. The data bolsters our proposed model of GH-GHR axis as aregulator of drug resistance in GH-responsive or GHR-expressing humancancers (FIG. 49 ). The effects of GHR-antagonist in reversing themechanisms of drug resistance in human liver cancer cells, and the roleof autocrine GH-GHR loop in driving drug resistance in human melanoma,supports our claim of sensitizing cancer cells to the effect ofanti-cancer therapy in combination with methods of GHR antagonism.

While the present invention was illustrated by the description of one ormore embodiments thereof, and while the embodiments have been describedin considerable detail, they are not intended to restrict or in any waylimit the scope of the appended claims to such detail. Additionaladvantages and modifications will readily appear to those skilled in theart. The invention in its broader aspects is therefore not limited tothe specific details, representative product and method, andillustrative examples shown and described. Accordingly, departures maybe made from such details without departing from the scope of thegeneral inventive concept embraced by the following claims.

What is claimed is:
 1. A method of treating cancer in a subject havingcancer cells, said cancer cells possessing at least one growth hormonereceptor, comprising: controlling an action of the growth hormonereceptor, wherein the controlling an action of the growth hormonereceptor includes knock down of the growth hormone receptor.
 2. Themethod of claim 1, wherein the subject is a human.
 3. The method ofclaim 1, wherein the cancer is at least one of breast cancer, colorectalcancer, prostate cancer, hepatic cell carcinoma, and melanoma.
 4. Themethod of claim 1, wherein the knock down of the growth hormone receptoris performed by siRNA mediated knock down.
 5. The method of claim 4,wherein the knock down of the growth hormone receptor is anti-sense RNAdirected against the growth hormone receptor.
 6. The method of claim 4,wherein the knock down of the growth hormone receptor is caused by anantibody specific to the growth hormone receptor.
 7. A method oftreating cancer in a subject having cells possessing at least one growthhormone receptor, comprising: controlling an action of the growthhormone receptor; and administering a sub-EC₅₀ dose of at least oneanti-tumor drug.
 8. The method of claim 7, wherein the anti-tumor drugis selected from the group consisting of cisplatin, doxorubicin,oridonin, paclitaxel, and vemurafenib.
 9. The method of claim 7, whereinthe subject is a human.
 10. The method of claim 7, wherein the cancer isat least one of breast cancer, colorectal cancer, prostate cancer,hepatic cell carcinoma, and melanoma.
 11. The method of claim 7, whereinthe controlling an action of the growth hormone receptor includes knockdown of the growth hormone receptor.
 12. The method of claim 11, whereinthe knock down of the growth hormone receptor is performed by siRNAmediated knock down.
 13. The method of claim 11, wherein the knock downof the growth hormone receptor is anti-sense RNA directed against thegrowth hormone receptor.
 14. The method of claim 11, wherein the knockdown of the growth hormone receptor is caused by an antibody specific tothe growth hormone receptor.
 15. The method of claim 7, wherein thecontrolling an action of the growth hormone receptor is caused byinhibiting growth hormone action.
 16. The method of claim 15, whereinthe inhibiting growth hormone action is caused by antibodies directedagainst growth hormone.
 17. A method of treating cancer in a subjecthaving cancer cells, said cancer cells possessing at least one growthhormone receptor, comprising: controlling an action of the growthhormone receptor, wherein the controlling an action of the growthhormone receptor is caused by inhibiting growth hormone action.
 18. Themethod of claim 17, wherein the inhibiting the growth hormone action iscaused by antibodies directed against growth hormone.
 19. The method ofclaim 17, wherein the inhibiting the growth hormone action is caused byantibodies directed against growth hormone receptor.
 20. The method ofclaim 17, wherein the subject is a human.
 21. The method of claim 17,wherein the cancer is at least one of breast cancer, colorectal cancer,prostate cancer, hepatic cell carcinoma, and melanoma.
 22. A method oftreating cancer in a subject having cancer cells, said cancer cellspossessing at least one growth hormone receptor, comprising: reducingserum insulin-like growth factor 1 (IGF1) levels below the normal serumIGF1 level of the subject.
 23. The method of claim 22, wherein thereducing of serum IGF1 levels is performed by controlling an action ofthe growth hormone receptor.
 24. A method of maintaining an anti-tumordrug in cancer cells of a subject, comprising: controlling an action ofat least one growth hormone receptor in said cancer cells, wherein thecontrolling of an action of the growth hormone receptor includes: a.knock down of the growth hormone receptor; b. inhibiting growth hormoneaction via antibodies directed against growth hormone; or c. inhibitinggrowth hormone action via antibodies directed against the growth hormonereceptor.
 25. The method of claim 24, wherein the anti-tumor drug isselected from the group consisting of cisplatin, doxorubicin, oridonin,paclitaxel, and vemurafenib.
 26. The method of claim 24, wherein thesubject is a human.
 27. The method of claim 24, wherein the cancer cellsare attributable to at least one of breast cancer, colorectal cancer,prostate cancer, hepatic cell carcinoma, and melanoma.
 28. The method ofclaim 24, wherein the controlling an action of the growth hormonereceptor includes knock down of the growth hormone receptor, and whereinthe knock down of the growth hormone receptor is performed by siRNAmediated knock down.
 29. The method of claim 26, wherein the knock downof the growth hormone receptor is anti-sense RNA directed against thegrowth hormone receptor.
 30. The method of claim 26, wherein the knockdown of the growth hormone receptor is caused by an antibody specific tothe growth hormone receptor.
 31. The method of claim 24, wherein thecontrolling an action of the growth hormone receptor is caused byinhibiting growth hormone action.
 32. The method of claim 31, whereinthe inhibiting the growth hormone action is caused by antibodiesdirected against growth hormone.